This is a draft pull request to experiment with ShadowRealms.

Findings:

• The current implementation in Node.js is still experimental behind a flag --experimental-shadow-realm: ShadowRealm Integration nodejs/node#42528
  • Memory leaks are possible: memory leak in shadow realms nodejs/node#47353
  • node:module is not (yet?) available, meaning hooks (like CSS support) are not supported
• Only primitive values and functions can be transferred between global context and ShadowRealm. Meaning only e.g. string, number, boolean, null, undefined and Function, but not an object, Promise or Array.

Questions:

• Should lit provide utility for using ShadowRealms?
• If yes, should the rendering be done fully inside the ShadowRealm (like render-inside-shadow-realm_test.ts) or via tranfer (like render-via-shadow-realm_test.ts)?