feat(supported-version): add user-defined kind (#28)

`kind` is a new input property for the `supported-version` action which
allows one to define what specific versions of Magento they support.

Currently, `kind` supports `latest`, `currently-supported`, and `custom`. See the
README for `supported-version` if you want more specifics

.github/workflows/_internal_test_actions.yaml

@@ -0,0 +1,29 @@
+name: Test Actions
+
+on:
+  push:
+    branches:
+    - main
+    paths:
+    - ".github/workflows/_internal-supported-version.yaml"
+    - "supported-version/**"
+    - "!(**/*.md)"
+  pull_request:
+    branches:
+    - main
+    paths:
+    - ".github/workflows/_internal-supported-version.yaml"
+    - "supported-version/**"
+    - "!(**/*.md)"
+
+jobs:
+  unit-test:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    
+    - run: npm ci
+      shell: bash
+
+    - run: npm test
+      shell: bash