fix: update actions/cache and README example (#38)

* fix: actions/cache

The actions/cache library has sunset all versions below 4.0.0, this bumps
it to 4.0.3. It is intended to be a drop in replacement and api compatible.

fixes #37

* docs: Update Example

The format for actions is required to be @[ref/tag/version] now. This updates the
example to reflect that.

fixes #30

Author: techman83

README.md

@@ -28,7 +28,7 @@ jobs:
           fi
       - name: Validate workflows
         if: steps.check-for-changed-workflows.outputs.any_changed == 'true'
-        uses: dsanders11/json-schema-validate-action
+        uses: dsanders11/json-schema-validate-action@1.2.0
         with:
           schema: https://json.schemastore.org/github-workflow.json
           files: .github/workflows/**.yml