Switch to monthly release cadence

We'd like to start releasing monthly so that we don't fall quite so far behind... based on past commit frequency, most of these releases will only contain merged  PR's bumping our deps, but this way we find out quickly if a dep breaks our action.

.github/workflows/release-bump-version.yml

@@ -1,6 +1,8 @@
 name: Release - Bump Version
 
-on:
+on:  # yamllint disable-line rule:truthy
+  schedule:
+    - cron: '0 0 1 * *'
   workflow_dispatch:
     inputs:
       version_type:
@@ -36,8 +38,7 @@ jobs:
           node-version-file: .nvmrc
 
       - name: Bump the version
-        # Currently we don't run via `schedule` trigger since this repo isn't active enough.
-        # However, if that ever changes, it will run with no inputs, so version_type will default to 'minor'
+        # Cron runs with no inputs, so version_type will default to 'minor'
         run: |
           NEW_VERSION=$(bin/bump-version ${{ github.event.inputs.version_type || 'minor' }})
           echo "New version is: $NEW_VERSION"