Removed trailing whitespace. Add lint script

Signed-off-by: Davide Scano <[email protected]>

.github/workflows/spec.yml

@@ -17,7 +17,7 @@ jobs:
     - uses: actions/checkout@v3
     - name: Run linter
       run: |
-        ./tools/asciidoc lint.py docs/v1/P4Runtime-Spec.adoc
+        ./tools/asciidoclint.py docs/v1/P4Runtime-Spec.adoc
 
   build-spec:
     runs-on: [ubuntu-latest]

CONTRIBUTING.md

@@ -6,4 +6,7 @@ All developers must have signed the [P4.org](http://p4.org) CLA.
 
 ### AsciiDoc style checker
 
-The P4Runtime specification is written using [AsciiDoc](https://docs.asciidoctor.org/). 
+The P4Runtime specification is written using [AsciiDoc](https://docs.asciidoctor.org/).
+We provide a lint tool to catch basic formatting issues and try to keep the spec uniform. 
+The lint tool will be run as part of CI and patches cannot be merged until it returns success. You can
+run the lint tool locally with `./tools/asciidoclint.py`.