docs(npm): update node requirements

[jsjoeio]

This PR fixes #2745 by adding extra information regarding Node.js requirements.

TODOS

• open separate issue for pre-install script that checks node version [dev]: pre-install script that checks dependencies #2807
• verify that v10 node works with code-server Couldn't get v10 Node to play nicely with code-server.
• verify that v14 node works with code-server
• issues with v15 as well
• update docs

How I tested versions of node:

1. nvm install 14
2. rm -rf node_modules
3. yarn
4. cd lib/vscode && npm rebuild
5. yarn watch
6. Navigate to localhost:8080 and see if code-server works

[code-asher]

Thoughts on whether we should have a pre-install script that forces the correct version of Node?

Also I'm not sure v10 or v14 works so we should definitely test them. If not then we'll want to restrict to v12 only.

[jsjoeio]

Thoughts on whether we should have a pre-install script that forces the correct version of Node?

Great idea! I think that could come in a separate PR. I'll open an issue for it. There's one open here: #2807

Also I'm not sure v10 or v14 works so we should definitely test them. If not then we'll want to restrict to v12 only.

Good call. Let me move to draft and test.