Improve issue templates & add PR template (#7051)

* improved feature suggestion template

* added test case chapter to bug report template

* PR wording

* added PR template

* improved formatting in issue template

* removed checkbox for concept due to new GH discussions process

* improved wording

* improved PR todo list

* amended PR checklist; minor rewording

* removed duplicate wording

* add securtiy check section to contribution guide

.github/ISSUE_TEMPLATE/---2-feature-request.md

@@ -7,14 +7,28 @@ assignees: ''
 
 ---
 
-**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 [...]
+### New Feature / Enhancement Checklist
+<!--
+    Please check the following boxes [x] before submitting your issue.
+    Click the "Preview" tab for better readability.
+    Thanks for contributing to Parse Server!
+-->
 
-**Describe the solution you'd like**
-A clear and concise description of what you want to happen.
+- [ ] I am not disclosing a [vulnerability](https://github.com/parse-community/parse-server/blob/master/SECURITY.md).
+- [ ] I am not just asking a [question](https://github.com/parse-community/.github/blob/master/SUPPORT.md).
+- [ ] I have searched through [existing issues](https://github.com/parse-community/parse-server/issues?q=is%3Aissue).
 
-**Describe alternatives you've considered**
-A clear and concise description of any alternative solutions or features you've considered.
+### Current Limitation
+<!-- Which current limitation is the feature or enhancement addressing? -->
 
-**Additional context**
-Add any other context or screenshots about the feature request here.
+### Feature / Enhancement Description
+<!-- What is the concept of the functionality and how should it be implemented? -->
+
+### Example Use Case
+<!-- What is an example use case in steps (1. / 2. / 3. / etc.) that describes the functionality? -->
+
+### Alternatives / Workarounds
+<!-- Which alternatives or workarounds exist currently? -->
+
+### 3rd Party References
+<!-- Have you seen a similar functionality provided somewhere else? -->