Expand readme to include codeql-path output example

Also add example from README into workflow to confirm it is accurate.

Author: Simon Engledew

.github/workflows/codeql.yml

@@ -15,7 +15,11 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: ./init
+      id: init
       with:
         languages: javascript
         config-file: ./.github/codeql/codeql-config.yml
+    # example from README.md
+    - name: Print CodeQL Version
+      run: ${{steps.init.outputs.codeql-path}} version --format=json
     - uses: ./analyze

README.md

@@ -125,10 +125,24 @@ By default, this will override any queries specified in a config file. If you wi
     queries: +<local-or-remote-query>,<another-query>
 ```
 
-### CodeQL Path
+### Calling CodeQL Directly
 
 The `init` action makes the path to CodeQL available as the output `codeql-path`.
 
+With this you can access the `codeql` binary:
+
+<!-- this example is run via .github/workflows/codeql.yml -->
+```yaml
+- name: Initialize CodeQL
+  uses: github/codeql-action/init@v1
+  id: init
+  with:
+    languages: javascript
+
+- name: Print CodeQL Version
+  run: ${{steps.init.outputs.codeql-path}} version --format=json
+```
+
 ## Troubleshooting
 
 Read about [troubleshooting code scanning](https://help.github.com/en/github/finding-security-vulnerabilities-and-errors-in-your-code/troubleshooting-code-scanning).