### What problem were solved in this pull request?

Problem: close #229 
当前的词法分析语法分析非常简单，那当遇到比较复杂的词法分析语法分析题目，比如表达式，有些同学就难以入手

### What is changed and how it works?
增加一个支持四则运算的功能，关键字是calc，虽然与标准的SQL不同，但是可以作为学习表达式入门使用。
使用示例：
```
(base) build_debug $ ./bin/observer -f ../etc/observer.ini -P cli
Successfully load ../etc/observer.ini
miniob > calc 2*(2*(2+3));
2*(2*(2+3))
20

miniob > calc (1+2) * (2 * (20+ -(5*1)))
(1+2) * (2 * (20+ -(5*1)))
90

miniob > calc 1, 2, 3;
1 | 2 | 3
1 | 2 | 3

miniob > calc 1 + 2 - 3+4;
1 + 2 - 3+4
4

miniob > calc 2* 4;
2* 4
8

miniob > calc 1, 2, 3;
1 | 2 | 3
1 | 2 | 3

miniob > calc 1 + 2 - 3+4;
1 + 2 - 3+4
4

miniob > calc 2* 4;
2* 4
8
```

更新readme链接

### What problem were solved in this pull request?

Problem:
readme文档内容较多

### What is changed and how it works?
删掉几个链接

### Other information

### What problem were solved in this pull request?

Issue Number: ref #165 
ref #174 

Problem:
一些文档需要优化

### What problem were solved in this pull request?

Issue Number: close #162 

Problem:
当前的observer启动流程和调试方法比较繁琐，必须使用客户端服务端的方式，先启动服务端程序，再使用客户端启动调试

### What is changed and how it works?
observer可以直接启动，不监听tcp或unix socket，直接通过终端/控制台输入命令并执行，极大的方便了调试

### Other information
新的启动方法：
./bin/observer -P cli -f ../etc/observer.ini

### What problem were solved in this pull request?

Problem:
当前生成的github pages不太整洁方便，可以优化一下

### What is changed and how it works?
改用mdbook生成文档，并整理文档目录，调整链接

### What problem were solved in this pull request?

Issue Number: close #188 

Problem:
利用doxygen将代码注释生成文档

### What is changed and how it works?
修改github action，增加doxygen生成文档，并gihtub pages部署发布

### Other information

### What problem were solved in this pull request?

Issue Number: close #175 

Problem:
github page 构建失败
看到报错信息：
```
googletest/docs/assets/css/style.scss File to import not found or unreadable
```
本来miniob的pages与子模块是无关的，看github page
action的逻辑是checkout了子模块，而这个子模块在这里有点问题。

### What is changed and how it works?
把github pages改成github action模式构建，并修改checkout的submodules参数为false，即不拉子模块。
这里只是修改一些文档链接，gitub page相关的commit：

https://github.com/oceanbase/miniob/commit/8a33f5219d7ed27797d49dc2a9bfd945dcd0d327

### Other information

### What problem were solved in this pull request?

Issue Number: close #152 

Problem:
增加gitpod 开发说明

### What is changed and how it works?

### Other information

优化Docker开发环境：
- docker镜像使用zsh；
- 自动初始化vscode开发调试配置环境；
- 容器中开启ssh服务，方便远程开发；
- 可以在构建镜像时clone自己的代码；
- 提供了丰富详细的使用文档。

2022 oceanbase competition

增加MiniOB介绍、训练营输出约定、SQL词法语法解析文档

fix a typo in docker command

在readme中 增加数据库讲义链接