Reconstruct necessary action workflows & Dependabot rules (#17)

.github/dependabot.yml

@@ -0,0 +1,40 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: weekly
+    labels:
+      - "infra"
+    reviewers:
+      - regginator
+    commit-message:
+      prefix: "ci"
+
+  - package-ecosystem: nuget
+    directory: /
+    open-pull-requests-limit: 10
+    schedule:
+      interval: daily
+    labels:
+      - "infra"
+    reviewers:
+      - regginator
+    commit-message:
+      prefix: nuget
+    groups:
+      Avalonia:
+        patterns:
+          - "*Avalonia*"
+      Silk.NET:
+        patterns:
+          - "Silk.NET*"
+      OpenTK:
+        patterns:
+          - "OpenTK*"
+      SixLabors:
+        patterns:
+          - "SixLabors*"
+      NUnit:
+        patterns:
+          - "NUnit*"