Possible to support these keys in `README.md` YAML front matter?

[dmalan]

lab50:
  cmd: CMD
  files:
    - foo.c
    - bar.c
  port: PORT
  readme: README
  window:
    - browser
    - terminal
    - x

whereby:

• CMD is the command to run in the terminal; if not provided, terminal should use default; it is an error to provide cmd but not terminal
• files is an array of files to open in the editor, from left to right, with the leftmost tab foregrounded ultimately
• readme is the URL via which to autoupdate README.md
• browser embeds a browser to the right of the editor and console, full height; it's an error to use x too
• terminal embeds a single terminal window in the console
• x embeds an X window to the right of the editor and console, full height; it's an error to use browser too
• PORT is the TCP port with which to configure an embedded browser (on localhost); it is an error to provide port but not browser; defaults to 8080

[dmalan]

This is inspired by https://cs50.readthedocs.io/lab/, with these differences:

• A local or remote README.md is now required; no README-less labs.
• No need to specify editor anymore.

I don't love the readme key at the moment, since it feels redundant for README.md to exist locally and just get overwritten by a remote copy. But I'm not sure we need to generalize autoupdates to support files besides README.md.

If we were to move all this YAML to the top of README.md itself, whereby it could be contained in YAML front matter instead of in .cs50.yml, that might be cleaner, if we're requiring that README.md exist anyway. Feels a bit redundant for .cs50.yml also to exist. But that would then start to drift from our implementations of submit50 and check50. Then again, this .cs50.yml is being used locally, not remotely in a repo, so it's already a bit different; we haven't distributed .cs50.yml files to students before.

[dmalan]

If we were to move the YAML to README.md instead, the top of the file could instead look like:

---
cmd: CMD
files:
  - foo.c
  - bar.c
port: PORT
url: URL
window:
  - browser
  - terminal
  - x
---
# README
...

where URL would be a value like https://github.com/cs50/lab50.vsix/blob/main/lab_demo/README.md or https://raw.githubusercontent.com/cs50/lab50.vsix/main/lab_demo/README.md.

This way, too, it would suffice to check for the presence of a README.md in a dir, to decide whether to show Open in CS50 Lab.

If there's no YAML present, defaults could be:

files: []
window:
  - terminal

[rongxin-liu]

https://github.com/cs50/lab50.vsix/commit/d08db648d99a5fe5564f2a5ab178f80f0c386c8e