add issue template (#4161)

.github/ISSUE_TEMPLATE/-------------other-general-issues.md

+---
+name: "\U0001F516  其他通用问题 / Other General Issues"
+about: 提出其他问题 / Suggest other general issues
+title: "[Other General Issues]"
+labels: ''
+assignees: ''
+
+---
+
+**PaddleDetection team appreciate any suggestion or problem you delivered~**
+
+## Checklist:
+
+1. 查找历史相关issue寻求解答/I have searched related issues but cannot get the expected help.
+2. 翻阅[FAQ](https://paddledetection.readthedocs.io/FAQ.html) /I have read the [FAQ documentation](https://paddledetection.readthedocs.io/FAQ.html) but cannot get the expected help.
+
+## 描述问题/Describe the bug
+A clear and concise description of what the bug is.
+
+## 复现/Reproduction
+
+1. 您使用的命令是？/What command or script did you run?
+
+```none
+请填写命令/A placeholder for the command.
+```
+2. 您是否更改过代码或配置文件？您是否理解您所更改的内容？还请您提供所更改的部分代码。/Did you make any modifications on the code or config? Did you understand what you have modified? Please provide the codes that you modified.
+
+3. 您使用的数据集是？/What dataset did you use?
+
+4. 请提供您出现的报错信息及相关log。/Please provide the error messages or relevant log information.
+
+## 环境/Environment
+1. 请提供您使用的Paddle和PaddleDetection的版本号/Please provide the version of Paddle and PaddleDetection you use：
+
+2. 如您在使用PaddleDetection的同时还在使用其他产品，如PaddleServing、PaddleInference等，请您提供其版本号/ Please provide the version of any other related tools/products used, such as the version of PaddleServing and etc：
+
+3. 请提供您使用的操作系统信息，如Linux/Windows/MacOS /Please provide the OS information, e.g., Linux：
+
+4. 请问您使用的Python版本是？/ Please provide the version of Python you used.
+
+5. 请问您使用的CUDA/cuDNN的版本号是？/ Please provide the version of CUDA/cuDNN you used.
+
+
+如果您的issue是关于安装或环境，您可以先查询[安装文档](https://github.com/PaddlePaddle/PaddleDetection/blob/release/2.1/docs/tutorials/INSTALL_cn.md)尝试解决~
+
+If your issue looks like an installation issue / environment issue,
+please first try to solve it yourself with the instructions in
+https://github.com/PaddlePaddle/PaddleDetection/blob/release/2.1/docs/tutorials/INSTALL.md

.github/ISSUE_TEMPLATE/------------feature-request.md

+---
+name: "\U0001F680  新功能需求 / Feature Request"
+about: 提出一个新的功能需求或改进建议 / Suggest an improvement for PaddleDetection
+title: "[Feature Request]"
+labels: ''
+assignees: ''
+
+---
+
+## 🚀  新功能/Feature
+
+PaddleDetection欢迎大家以清晰简洁的语言提出新功能需求。
+
+A clear and concise description of the feature proposal.
+
+## 需求原因&示例/Motivation & Examples
+
+请描述这个需求的必要性。
+
+Tell us why the feature is useful.
+
+请描述这个需求可实现的具体功能，如果可以，辛苦您提供相关代码实现效果。
+
+Describe what the feature would look like, if it is implemented.
+Best demonstrated using **code examples** in addition to words.
+
+## 📣 注意/Note
+
+PaddleDetection仅添加通用性较高的新功能/特性。
+
+We only consider adding new features if they are relevant to many users.
+
+如果您需要论文中的模型能力，PaddleDetection会优先考虑与目标检测强相关且意义较大的论文。
+
+If you request implementation of research papers -- we only consider papers that have enough significance and prevalence in the object detection field.
+
+比如“让XX功能更快”类似的需求不能作为一个有效需求，需要更具体的描述，如“创建一个具体XX工具/功能，让XX更快”即是一个有效需求。
+
+"Make X faster/accurate" is not a valid feature request. "Implement a concrete feature that can make X faster/accurate" can be a valid feature request.
+
+PaddleDetection感谢您的支持，我们期待您提出新功能需求！
+
+Thanks for your suggestions!

.github/ISSUE_TEMPLATE/-----------documentation-improvement.md

+---
+name: "\U0001F4D6  文档优化 / Documentation Improvement"
+about: 对现有的文档教程提出修改建议 / Suggest an improvement about existing documentation or tutorials
+  in PaddleDetection.
+title: "[Document Improvement]"
+labels: ''
+assignees: ''
+
+---
+
+## 📖  文档优化/Documentation Improvement
+
+**请简单说明文档存在问题/Please provide a concise and brief description of the documentation problem:**
+
+**请提供有问题的文档部分截图及链接/Please provide the screen shoot and the link of the document:**

.github/ISSUE_TEMPLATE/------bug---bug-report.md

+---
+name: "\U0001F41B  提出Bug / Bug Report"
+about: 提出PaddleDetection使用中存在的Bug / Report a bug in PaddleDetection
+title: "[BUG]"
+labels: ''
+assignees: ''
+
+---
+
+**PaddleDetection team appreciate any suggestion or problem you delivered~**
+
+## Checklist:
+
+1. 查找历史相关issue寻求解答/I have searched related issues but cannot get the expected help.
+2. 翻阅[FAQ](https://paddledetection.readthedocs.io/FAQ.html) /I have read the [FAQ documentation](https://paddledetection.readthedocs.io/FAQ.html) but cannot get the expected help.
+3. 确认bug是否在新版本里还未修复/The bug has not been fixed in the latest version.
+
+## 描述问题/Describe the bug
+A clear and concise description of what the bug is.
+
+## 复现/Reproduction
+
+1. 您使用的命令是？/What command or script did you run?
+
+```none
+请填写命令/A placeholder for the command.
+```
+2. 您是否更改过代码或配置文件？您是否理解您所更改的内容？还请您提供所更改的部分代码。/Did you make any modifications on the code or config? Did you understand what you have modified? Please provide the codes that you modified.
+
+3. 您使用的数据集是？/What dataset did you use?
+
+4. 请提供您出现的报错信息及相关log。/Please provide the error messages or relevant log information.
+
+## 环境/Environment
+1. 请提供您使用的Paddle和PaddleDetection的版本号/Please provide the version of Paddle and PaddleDetection you use：
+
+2. 如您在使用PaddleDetection的同时还在使用其他产品，如PaddleServing、PaddleInference等，请您提供其版本号/ Please provide the version of any other related tools/products used, such as the version of PaddleServing and etc：
+
+3. 请提供您使用的操作系统信息，如Linux/Windows/MacOS /Please provide the OS information, e.g., Linux：
+
+4. 请问您使用的Python版本是？/ Please provide the version of Python you used.
+
+5. 请问您使用的CUDA/cuDNN的版本号是？/ Please provide the version of CUDA/cuDNN you used.
+
+
+如果您的issue是关于安装或环境，您可以先查询[安装文档](https://github.com/PaddlePaddle/PaddleDetection/blob/release/2.1/docs/tutorials/INSTALL_cn.md)尝试解决~
+
+If your issue looks like an installation issue / environment issue,
+please first try to solve it yourself with the instructions in
+https://github.com/PaddlePaddle/PaddleDetection/blob/release/2.1/docs/tutorials/INSTALL.md