[Feature]: Configurable CDN for playwright install

[jp-gr]

🚀 Feature Request

Would you be open to making the CDN configurable via an environment variable?

Example

PLAYWRIGHT_CDN_URL="xxx" python -m playwright install chromium

Motivation

We operate in an airgapped environment so being able to point at a corporate proxy would be very handy!

Seems others have had this issue in the past - e.g. #574