chore: replace Renovate with Dependabot (#20)

.github/dependabot.yml

@@ -0,0 +1,39 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "composer"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    commit-message:
+      prefix: "chore(deps/composer):"
+    labels:
+      - "t-dependencies"
+      - "pkg-composer"
+    groups:
+      mediawiki:
+        patterns:
+          - "mediawiki/*"
+      php-parallel-lint:
+        patterns:
+          - "php-parallel-lint/*"
+      phpunit:
+        patterns:
+          - "ockcyp/covers-validator"
+          - "phpunit"
+    open-pull-requests-limit: 4
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    commit-message:
+      prefix: "chore(deps/actions):"
+    labels:
+      - "t-dependencies"
+      - "pkg-gh-actions"
+    open-pull-requests-limit: 4