Add gitlab-cdn.net to Web IDE CSP

• feat: Use `cdn.web-ide.gitlab-static.net` for w... (gitlab-web-ide!196 - merged)
• Add gitlab-cdn.net to Web IDE CSP (!122812 - closed)

What does this MR do and why?

This MR adds gitlab-cdn.net to the Web IDE CSP. This is to support removing our runtime dependency on vscode-cdn.net.

See also:

• #414488 (closed)
• gitlab-web-ide!196 (merged)

Screenshots or screen recordings

How to set up and validate locally

1. Run yarn install
2. (TEMPORARY until gitlab-cdn.net is available) Follow these instructions in the gtilab-web-ide project.
3. Start GDK and visit the Web IDE for any project - verify that vscode-cdn.net is not hit and features like Preview Markdown work.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.