moved node version section in README to advanced usage

added link to README
* migrated contents of version-file-workflow.yml to versions.yml
* further refactored parseNodeVersionFile() & tests
* removed type annotations in catch ()

.github/workflows/versions.yml

@@ -78,6 +78,17 @@ jobs:
         run: __tests__/verify-node.sh "${{ matrix.node-version }}"
         shell: bash
 
+  version-file:
+    runs-on: ${{ matrix.os }}
+      strategy:
+        matrix:
+          os: [ubuntu-latest, windows-latest, macos-latest]
+      steps:
+        - uses: actions/checkout@v2
+        - name: Setup node test
+          uses: ./
+          with:
+            node-version-file: '.nvmrc'
   node-dist:
     runs-on: ${{ matrix.os }}
     strategy: