Ensure all NPM packages have readmes included in their builds

[bgrgicak]

Motivation for the change, related issues

This PR ensures all public package builds include a README.md file,
because some of our NPM packages don't include a readme on the npmjs.com package page.

The readmes exist in project folders, but before this PR they were not added to the built version of the package.

Implementation details

Add build:README step to these public packages:

• @php-wasm/cli
• @php-wasm/progress
• @php-wasm/scopes
• @php-wasm/web-service-worker
• @wp-playground/blueprints
• @wp-playground/cli
• @wp-playground/client
• @wp-playground/components
• @wp-playground/remote
• @wp-playground/sync

Testing Instructions (or ideally a Blueprint)

• Remove the dist folder if it exists
• Run npm run build
• Check that all PHP-wasm builds have a README.md

find dist/packages/php-wasm -mindepth 1 -maxdepth 1 -type d '!' -exec test -e '{}/README.md' \; -print

• The above command should only return dist/packages/php-wasm/out-tsc-phpwasm-node which isn't a package
• Check that all Playground builds have a README.md

find dist/packages/playground -mindepth 1 -maxdepth 1 -type d '!' -exec test -e '{}/README.md' \; -print

• The above command should only return dist/packages/playground/website which isn't a published package

[adamziel]

Nicely done!