Playwright support

[lucatume]

This PR adds the playwright command to allow interacting with the node_modules/.bin/playwright binary in the slic container.
The command will not deal with requiring or installing Playwright or its dependencies, but will add a p alias in the stack.

E.g. to set up Playwright from scratch in a project:

slic npm init playwright@latest
slic playwright install chromium
slic playwright test

The same could be done from within slic shell:

$ npm init playwright@latest
$ p install chromium
$ p test

Finally, the PR adds the less binary to the slic container to allow for complete output of wp <command> --help.