Update issue templates

.github/ISSUE_TEMPLATE/bug-report.md

@@ -2,7 +2,7 @@
 name: Bug Report
 about: Create a report to help us improve
 title: ''
-labels: ''
+labels: bug
 assignees: ''
 
 ---

.github/ISSUE_TEMPLATE/feature-request.md

@@ -2,7 +2,7 @@
 name: Feature Request
 about: Suggest an idea for this project
 title: ''
-labels: ''
+labels: enhancement
 assignees: ''
 
 ---

.github/ISSUE_TEMPLATE/general-questions.md

@@ -2,7 +2,7 @@
 name: General Questions
 about: General questions about TDengine's usage, user experiences, milestones etc.
 title: ''
-labels: ''
+labels: help wanted, question
 assignees: ''
 
 ---

.github/ISSUE_TEMPLATE/performance-related-questions.md

@@ -2,7 +2,7 @@
 name: Performance-related Questions
 about: Any questions related to TDengine's performance.
 title: ''
-labels: ''
+labels: performance
 assignees: ''
 
 ---