chore: update contribution guidelines and pull request template

### Changed
- Enhanced the `CONTRIBUTING.md` file to include instructions for linking issues in the changelog entries.
- Streamlined the `.github/PULL_REQUEST_TEMPLATE.md` by removing unnecessary sections and clarifying the checklist items for contributors.

### Added
- Included a Contribution Guide link and a reminder for contributors to update the `CHANGELOG.md` under the `[NextRelease]` section in the pull request template.

Author: Artemonim

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,6 @@
 <!--
 Thank you for contributing to AgentDocstringsGenerator!
 
-Please provide a clear and concise description of your changes.
 If your PR is a work in progress, please mark it as a draft.
 -->
 
@@ -20,34 +19,13 @@ Please check the box that best describes the nature of your change.
 -   [ ] 🎨 **Style**: Changes that do not affect the meaning of the code (white-space, formatting, etc.).
 -   [ ] ⏪ **Revert**: Reverts a previous commit.
 
----
-
-## Related Issue
-
-<!--
-If this PR addresses a specific issue, please link it here.
-For example: `Fixes #123` or `Closes #123`.
-If there is no related issue, please state that.
--->
-
--   ***
-
-## Description
-
-<!--
-Provide a clear and concise summary of the changes.
-Explain the "what" and "why" of your contribution.
--->
-
--
-
 ## Checklist
 
 <!--
 Go over all the following points, and put an `x` in all the boxes that apply.
 -->
 
--   [ ] My code follows the style guidelines of this project.
--   [ ] I have performed a self-review of my own code.
+-   [ ] My changes follows the [Contribution Guide](CONTRIBUTING.md).
+-   [ ] I have updated `CHANGELOG.md` under the `[NextRelease]` section.
 -   [ ] New unit tests have been added to cover the changes.
--   [ ] Manual testing has been performed
+-   [ ] Manual testing has been performed to verify the changes.

CONTRIBUTING.md

@@ -75,16 +75,16 @@ This project uses a GitFlow-like branching model.
 
 ### Updating the Changelog
 
-For every change that affects the user, you must add an entry to the `CHANGELOG.md` file under the `[NextRelease]` section. Follow the format of existing entries.
+For every change that affects the user, you must add an entry to the `CHANGELOG.md` file under the `[NextRelease]` section. Follow the format of existing entries. If your pull request resolves an existing issue, please link it in the changelog entry `(fixes #123)` or `(closes #456)`).
 
 Example:
 
 ```markdown
 ## [NextRelease]
 
-### TypeOfChange
+### Fixed
 
--   **Your Awesome Feature**: A brief description of what you've added.
+-   **My Awesome Fix**: A brief description of what you've fixed (fixes #78).
 ```
 
 ## Release Process (for maintainers)