docs: e2e contribution documentation

Author: raphael-geffroy

CONTRIBUTING.md

@@ -95,6 +95,16 @@ Thanks to [PNPM Workspaces](https://pnpm.io/workspaces), you can also run these
   - `pnpm run check`: run the formatter, linter, and sort imports for **all** packages, and fails if any modifications
   - `pnpm run check --write`: run the formatter, linter, imports sorting for **all** packages, and write modifications
 
+### Working with e2e tests
+
+- `pnpm install`
+- `(cd ./apps/e2e && SYMFONY_REQUIRE=7.3.* symfony composer update)`
+Then you can run e2e commands:
+- per package: `pnpm exec playwright test --ui` (from the project root)
+- per package: `pnpm run test:browser` (from a given package)
+- globally : `pnpm run test:browser`
+
+
 ### Working on documentation
 
 Symfony UX documentation is written in ReStructuredText (`.rst`) and is located in the `docs/` directory