chore: Introduce changelog (#592)

* chore: Introduce changelog

Signed-off-by: Tom Kerkhove <[email protected]>

* Update PULL_REQUEST_TEMPLATE.md

Signed-off-by: Tom Kerkhove <[email protected]>

---------

Signed-off-by: Tom Kerkhove <[email protected]>

Author: tomkerkhove

.github/PULL_REQUEST_TEMPLATE.md

@@ -9,6 +9,7 @@ _Provide a description of what has been changed_
 ### Checklist
 
 - [ ] Commits are signed with Developer Certificate of Origin (DCO)
+- [ ] Changelog has been updated and is aligned with our [changelog requirements](https://github.com/kedacore/keda/blob/main/CONTRIBUTING.md#Changelog)
 - [ ] Any necessary documentation is added, such as:
   - [`README.md`](/README.md)
   - [The `docs/` directory](./docs)

Changelog.md

@@ -0,0 +1,44 @@
+# Changelog
+
+<!--
+    New changelog entries must be inline with our changelog guidelines.
+    Please refer to https://github.com/kedacore/keda/blob/main/CONTRIBUTING.md#Changelog to learn more.
+-->
+
+This changelog keeps track of work items that have been completed and are ready to be shipped in the next release.
+
+## History
+
+- [Unreleased](#unreleased)
+ 
+## Unreleased
+
+### Breaking Changes
+
+- TODO
+
+### New
+
+### Improvements
+
+- **General**: TODO ([#TODO](https://github.com/kedacore/http-add-on/issues/TODO))
+
+### Fixes
+
+- **General**: TODO ([#TODO](https://github.com/kedacore/http-add-on/issues/TODO))
+
+### Deprecations
+
+You can find all deprecations in [this overview](https://github.com/kedacore/http-add-on/labels/breaking-change) and [join the discussion here](https://github.com/kedacore/http-add-on/discussions/categories/deprecations).
+
+New deprecation(s):
+
+- TODO
+
+Previously announced deprecation(s):
+
+- TODO
+
+### Other
+
+- TODO