214187da

By: Michael Lynch <git@mtlynch.io>

Add Nix target for e2e/Playwright tests

check-bash, check-elixir, and check-frontend all have flake.nix
packages/checks entries, but run-browser-tests (the pre-commit hook's
Playwright suite) didn't, so nix flake check and
build-all-flake-targets never exercised it.