Add PR template for changelog automation (#1517)

* Update CONTRIBUTING.md and PR template

Signed-off-by: Sachin Sahu <75629410+SachinSahu431@users.noreply.github.com>

* Add examples in PR template

Signed-off-by: Sachin Sahu <75629410+SachinSahu431@users.noreply.github.com>

* Add examples in CONTRIBUTING.md

Signed-off-by: Sachin Sahu <75629410+SachinSahu431@users.noreply.github.com>

---------

Signed-off-by: Sachin Sahu <75629410+SachinSahu431@users.noreply.github.com>

.github/pull-request-template.md

@@ -0,0 +1,16 @@
+<!-- Refer to CONTRIBUTING.md for more details and examples.
+https://github.com/prometheus/client_golang/blob/main/CONTRIBUTING.md#how-to-fill-the-pr-template  
+-->
+### Describe your PR
+
+
+### What type of PR is this?
+
+<!-- Format: /kind followed by ONE of the type {fix, bugfix, enhancement, feature, feat, change, release-note-none} -->
+
+
+### Changelog Entry
+```release-note
+
+```
+<!-- Briefly describe any USER-FACING changes introduced in your PR. If your change should not appear in the changelog, write NONE. -->

CONTRIBUTING.md

@@ -1,5 +1,7 @@
 # Contributing
 
+Thank you for contributing to our project! Here are the steps and guidelines to follow when creating a pull request (PR).
+
 Prometheus uses GitHub to manage reviews of pull requests.
 
 * If you have a trivial fix or improvement, go ahead and create a pull request,
@@ -18,3 +20,55 @@ Prometheus uses GitHub to manage reviews of pull requests.
   Environments](http://peter.bourgon.org/go-in-production/#formatting-and-style).
 
 * Be sure to sign off on the [DCO](https://github.com/probot/dco#how-it-works)
+
+## How to fill the PR template
+
+### Describe your PR
+
+In this section, provide a clear and concise description of what your PR does. This helps reviewers understand the purpose and context of your changes.
+
+### What type of PR is this?
+
+Indicate the type of PR by adding one of the following options:
+
+- `/kind fix`
+- `/kind bugfix`
+- `/kind enhancement`
+- `/kind feature`
+- `/kind feat`
+- `/kind change`
+- `/kind release-note-none`
+
+If this change should not appear in the changelog, use `/kind release-note-none`.
+
+Example 1:
+```
+  ### What type of PR is this?
+  /kind feature
+```
+
+Example 2:
+```
+  ### What type of PR is this?
+  /kind release-note-none
+```
+
+### Changelog Entry
+
+Include a brief summary of your change for the changelog. This helps users understand what has been modified, added, or fixed in the project. If your change should not appear in the changelog, write `NONE`. Make sure to add only user-facing changes.
+
+Example 1:
+```
+	### Changelog Entry
+	```release-note
+	api: Switch to POST for `LabelNames`.
+	```
+```
+
+Example 2:
+```
+	### Changelog Entry
+	```release-note
+	NONE
+	```
+```