fix(ci): add release-please manifest

Author: fiji-flo

Diff for: .github/workflows/release_please.yml

@@ -15,5 +15,5 @@ jobs:
     steps:
       - uses: googleapis/release-please-action@v4
         with:
-          release-type: rust
           repo-url: mdn/rari
+          manifest-file: .release-please-manifest.json

Diff for: .release-please-manifest.json

@@ -0,0 +1,9 @@
+{
+  "bootstrap-sha": "eefc5a8d6dd623b6928fd99dc5681095a29cb633",
+  "bump-minor-pre-major": true,
+  "packages": {
+    ".": {
+      "release-type": "rust"
+    }
+  }
+}