fix dependabot.yml (#972)

Towards #971 
- #971 

The dependabot script appear broken. This copies the config from
maplibre-gl-js, which we know work.

## Launch Checklist

<!-- Thanks for the PR! Feel free to add or remove items from the
checklist. -->


 - [ ] Briefly describe the changes in this PR.
 - [ ] Link to related issues.
- [ ] Include before/after visuals or gifs if this PR includes visual
changes.
 - [ ] Write tests for all new functionality.
 - [ ] Add an entry to `CHANGELOG.md` under the `## main` section.

.github/dependabot.yml

@@ -1,14 +1,17 @@
+# 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://help.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
 version: 2
 updates:
-  - package-ecosystem: "npm"
-    directory: "/"
+  - package-ecosystem: "npm" # See documentation for possible values
+    directory: "/" # Location of package manifests
     schedule:
       interval: "daily"
-    open-pull-requests-limit: 2
+    open-pull-requests-limit: 20
     versioning-strategy: increase
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
       interval: "daily"
-    open-pull-requests-limit: 2
-    versioning-strategy: increase