Update issue templates

Template maintenance. 

- adding title prefix.
- adding examples to "additional context" section.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -32,3 +32,5 @@ If applicable, add screenshots to help explain your problem.
 
 **Additional context**
 Add any other context about the problem here.
+e.g. code snippet to reproduce the issue.
+e.g. stack trace, memory dump, debugger log, and many etc.

.github/ISSUE_TEMPLATE/documentation-issue.md

@@ -1,7 +1,7 @@
 ---
 name: Documentation issue
 about: Create a report to help us improve our documentation.
-title: ''
+title: "[DOC]"
 labels: documentation
 assignees: ''
 

.github/ISSUE_TEMPLATE/general-inquiry.md

@@ -1,7 +1,7 @@
 ---
 name: General inquiry
 about: Free form communication.
-title: ''
+title: "[Inquiry]"
 labels: question
 assignees: ''