[FIX] Dependabot not working

Dependabot did not work anymore.
This fixes and adds Docker as well.

Enable dependabot for most recent and supported branches:

This change enables Dependabot for all supported branches, by trying 
to consume dependabot settings 
[`target-branch`](https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#target-branch) together with 
[`commit-message.prefix`](https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#commit-message)

Fixes: #3168

.github/dependabot.yml

@@ -0,0 +1,50 @@
+version: 2
+updates:
+  -
+    package-ecosystem: "composer"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    allow:
+      - dependency-name: "solarium/solarium"
+    target-branch: "main"
+    commit-message:
+      prefix: "[TASK] 13.0.x-dev "
+  -
+    package-ecosystem: "docker"
+    directory: "/Docker/SolrServer"
+    schedule:
+      interval: "daily"
+    target-branch: "main"
+    commit-message:
+      prefix: "[TASK] 13.0.x-dev "
+
+  # For release-12.0.x
+  -
+    package-ecosystem: "composer"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    allow:
+      - dependency-name: "solarium/solarium"
+    target-branch: "release-12.0.x"
+    commit-message:
+      prefix: "[TASK] 12.0.x-dev "
+  -
+    package-ecosystem: "docker"
+    directory: "/Docker/SolrServer"
+    schedule:
+      interval: "daily"
+    target-branch: "release-12.0.x"
+    commit-message:
+      prefix: "[TASK] 12.0.x-dev "
+
+  # For release-11.6.x
+  -
+    package-ecosystem: "docker"
+    directory: "/Docker/SolrServer"
+    schedule:
+      interval: "daily"
+    target-branch: "release-11.6.x"
+    commit-message:
+      prefix: "[TASK] 11.6.x-dev "