DevKit updates (#406)

.github/ISSUE_TEMPLATE/Bug.md

@@ -4,6 +4,12 @@ about: Something is broken? 🔨
 labels: bug, unconfirmed
 ---
 
+<!--
+    Since no sonata-maintainer is using this bundle, there is no active support
+    on it. Therefore it's marked as abandoned and issues will be closed. Feel
+    free to make a PR instead if you want to keep this project up to date.
+-->
+
 <!--
     Before you open an issue, make sure this one does not already exist.
     Please also read the "guidelines for contributing" link above before posting.

.github/ISSUE_TEMPLATE/Feature.md

@@ -4,6 +4,12 @@ about: I have a suggestion (and may want to implement it 🙂)!
 labels: feature
 ---
 
+<!--
+    Since no sonata-maintainer is using this bundle, there is no active support
+    on it. Therefore it's marked as abandoned and issues will be closed. Feel
+    free to make a PR instead if you want to keep this project up to date.
+-->
+
 ## Feature Request
 
 <!-- Provide a summary of the feature. -->

README.md

@@ -22,6 +22,12 @@ Branch | Github Actions | Code Coverage | Documentation |
 3.x | [![Test][test_stable_badge]][test_stable_link] | [![Coverage Status][coverage_stable_badge]][coverage_stable_link] | [![Documentation Status][documentation_stable_badge]][documentation_stable_link] |
 4.x | [![Test][test_unstable_badge]][test_unstable_link] | [![Coverage Status][coverage_unstable_badge]][coverage_unstable_link] | [![Documentation Status][documentation_unstable_badge]][documentation_unstable_link] |
 
+## WARNING: This repository is abandoned
+
+There is no active support on it.
+
+Feel free to ask if you want to help to keep this project up to date.
+
 ## Documentation
 
 Check out the documentation on the [official website](https://docs.sonata-project.org/projects/SonataCacheBundle).