chore: added filter examples

CONTRIBUTING.md

@@ -62,11 +62,11 @@ If you observe following error running any of the test files that means you are
 - To fix errors always focus on passing all minimal tests first without running mainnet tests.
 - Spec tests often compare full expected vs actual states in JSON format.
 - A single logical error can cause many spec tests to fail. To focus on a single test at a time you can use vitest's option `--bail 1` to stop at the first failed test
-- To then run only that failed test you can run against a specific file as use vitest's filters to run only one case
+- To then run only that failed test you can run against a specific file as use vitest's filters option `-t <pattern>` to run only one case
 
 ```sh
 cd packages/beacon-node
-LODESTAR_PRESET=minimal yarn vitest --run --config vitest.config.spec.ts test/spec/presets/sanity.test.ts
+LODESTAR_PRESET=minimal yarn vitest --run --bail 1 --config vitest.config.spec.ts test/spec/presets/sanity.test.ts -t attester_slashing
 ```
 
 ## Docker