ci: group and rate-limit dependabot updates (#331)

Signed-off-by: krisztianfekete <git@krisztianfekete.org>

Author: krisztianfekete

.github/dependabot.yml

@@ -6,8 +6,32 @@ updates:
   - package-ecosystem: "cargo"
     directory: "/"
     schedule:
-      interval: "daily"
+      interval: "weekly"
+      day: "monday"
+    groups:
+      cargo-minor-patch:
+        patterns:
+          - "*"
+        update-types:
+          - "minor"
+          - "patch"
+      cargo-major:
+        patterns:
+          - "*"
+        update-types:
+          - "major"
+    open-pull-requests-limit: 2
+    cooldown:
+      default-days: 7
+
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
       interval: "monthly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+    open-pull-requests-limit: 1
+    cooldown:
+      default-days: 7