chore: lower dependabot noise (#121)

We have the Cargo.lock file checked in. This means that dependabot
opens PR for every version change. That creates a lot of noise. I
care about breaking new releases. This new config should hopefully
fix that.

Minor and patch releases should now be grouped into a single PR.

Author: vmx

.github/dependabot.yml

@@ -1,9 +1,17 @@
 version: 2
 updates:
+  # Non breaking changes will be grouped in a single PR. This way we can see
+  # on the CI if any minor update accidentally broke our code.
+  # Breaking changes will create individual PRs.
   - package-ecosystem: "cargo"
     directory: "/"
     schedule:
       interval: "daily"
+    groups:
+      minor-and-patch-updates:
+        patterns:
+          - "*"
+        update-types: ["minor", "patch"]
 
   - package-ecosystem: "github-actions"
     directory: "/"