Implement custom action to collect changes / matrix (#9)

.github/actions/collect-changed-charts/action.yml

@@ -0,0 +1,32 @@
+name: 'Changed charts'
+description: 'Collects the changed Helm charts and returns the lint/test matrix'
+inputs:
+  token:
+    description: >
+      GitHub token for GitHub API requests.
+    required: true
+    default: '${{ github.token }}'
+  chartsFolder:
+    description: >
+      Base folder containing all the charts
+    required: true
+    default: 'charts'
+  repoConfigFile:
+    description: >
+      Path to the repo config file that contains which charts
+      should be excluded from linting/testing.
+    required: true
+    default: '.ci/repo-config.yaml'
+outputs:
+  changedCharts:
+    description: >
+      An array of all the Helm charts that contain changes
+  chartsToInstall:
+    description: >
+      An array of the charts that should be installed
+  chartsToLint:
+    description: >
+      An array of the charts that should be linted
+runs:
+  using: 'node16'
+  main: 'dist/index.js'