add JS lint workflow

[JasonWeill]

Ran jlpm lint inside packages/jupyter-ai. This change fixes or suppresses all lint errors found.

Adds a new GitHub action to run lerna run lint on every pull request in this package. Note that the action doesn't run on this pull request.

This is prep work for #201, which should run lint on all PRs.

[3coins]

@JasonWeill
Thanks for creating this PR. You might also want to update the lint command in root package.json, so it points to jupyter_ai package.

lint: lerna run lint --stream --scope \"@jupyter-ai/core\"

[JasonWeill]

Should we add eslint to other packages in this repo with TypeScript code in them?

[3coins]

Should we add eslint to other packages in this repo with TypeScript code in them?

jupyter_ai is the only package with TS code. I think cookiecutter is not currently usable as is for providers.

[JasonWeill]

When running at the top level, it seems like code in the core package gets run:

(jupyter-ai) c889f3b5ce75:jupyter-ai jweill$ jlpm run lint
yarn run v1.21.1
$ jlpm && lerna run prettier && lerna run eslint
[1/4] 🔍  Resolving packages...
success Already up-to-date.
lerna notice cli v6.6.2

> @jupyter-ai/core:prettier

$ jlpm prettier:base --write --list-different
$ prettier "**/*{.ts,.tsx,.js,.jsx,.css,.json,.md}" --write --list-different

 ——————————————————————————————————————————————————————————————————————————————

 >  Lerna (powered by Nx)   Successfully ran target prettier for project @jupyter-ai/core (2s)
 
lerna notice cli v6.6.2

> @jupyter-ai/core:eslint

$ jlpm eslint:check --fix
$ eslint . --cache --ext .ts,.tsx --fix

 ——————————————————————————————————————————————————————————————————————————————

 >  Lerna (powered by Nx)   Successfully ran target eslint for project @jupyter-ai/core (1s)
 
✨  Done in 5.63s.

[JasonWeill]

Looks good! Thanks @dlqqq for your revisions. (I can't give a ship-it to this PR, since I'm still listed as the author.)