Add modular lint command

[NMinhNguyen]

See prior discussion in #90 and #108. Will require configurability to specify options such as the base branch (main / master) https://github.com/atlassian/changesets/blob/377f5c385ad9db4ff8458f159e2d452c39828567/packages/config/schema.json#L52-L56

[sebinsua]

I wrote two relevant comments within the previous PR:

(1)

Btw, as mentioned in chat, in terms of improving lint within an actual modular project (which this PR is not about), I'm starting to think that it'll be good to add a single modular lint [--all] command which does not support every single eslint option. Because if people really need to use these, they will still be able to skip us and call eslint themselves, and the whole point is to be opinionated.

(2)

I think my position on this is that we kind of aim to fulfill the 'pierceable abstraction' concept by implementing it in such a way that (1) all options are easily passable internally, but (2) the CLI API layer that wraps this is highly opinionated (for example, it might only support --all and --mergeBase=${branchName}).

[NMinhNguyen]

I just realised something. Using a naive approach of just calling the CLI (without chunking files like lint-staged does) can cause issues such as lint-staged/lint-staged#147 on Windows. Something to bear in mind for modular lint.

[sebinsua]

Within another issue @NMinhNguyen wrote:

It is also possible to define custom Jest runners: http://youtube.com/watch?v=U_IYuAXtJZ0

I actually quite like this idea with regards to improving the DX of other tools (e.g. modular lint).

[LukeSheard]

@cangarugula Let's target this for 1.2 using jest-runner-eslint by default.