[Issue Template] Add Validation (#3067)

* issue template update

- add  issue validation inspired by https://github.com/ChrisTitusTech/linutil/pull/459
- standardize capitalisation of characters in titles
- update feature request to use headers instead of bold text for titles

* use "I checked" for Issue validation

.github/ISSUE_TEMPLATE/bug_report.md

@@ -9,12 +9,11 @@ assignees: ''
 ## Describe the bug
 <!-- A clear and concise description of what the bug is. -->
 
-## To Reproduce
-Steps to reproduce the behavior:
+## Steps to reproduce
 1. Go to '...'
 2. Click on '....'
 3. Scroll down to '....'
-4. See error
+4. See the error.
 
 ## Expected behavior
 <!-- A clear and concise description of what you expected to happen. -->
@@ -24,3 +23,8 @@ Steps to reproduce the behavior:
 
 ## Additional context
 <!-- Add any other context about the problem here. -->
+
+## Issue validation
+- [ ] I checked for duplicate issues.
+- [ ] I checked for already existing discussions.
+- [ ] I checked for an already existing pull request addressing the issue.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -4,17 +4,21 @@ about: Suggest an idea for this project
 title: ''
 labels: 'enhancement'
 assignees: ''
-
 ---
 
-**Is your feature request related to a problem? Please describe.**
+## Is your feature request related to a problem? Please describe
 <!-- A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] -->
 
-**Describe the solution you'd like**
+## Describe the solution you'd like
 <!-- A clear and concise description of what you want to happen. -->
 
-**Describe alternatives you've considered**
+## Describe alternatives you've considered
 <!-- A clear and concise description of any alternative solutions or features you've considered. -->
 
-**Additional context**
+## Additional context
 <!-- Add any other context or screenshots about the feature request here. -->
+
+## Issue validation
+- [ ] I checked for duplicate issues.
+- [ ] I checked for already existing discussions.
+- [ ] I checked for an already existing pull request addressing the issue.