Update chokidar to v3

[polarathene]

Presently results in a warning about breakage on node v14 installs.

warning gatsby > babel-plugin-add-module-exports > chokidar@2.1.8: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
warning gatsby > babel-plugin-add-module-exports > chokidar > fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.

Benefits by the maintainer are mentioned here:

We've released Chokidar 3 in April. See my post on that: Chokidar 3: How to save 32TB of traffic every week with one NPM package

The changes are pretty big. First of all, the package is 16 times smaller and uses 15 dependencies instead of 201. We've switched to n-api, which means users won't download fsevents binaries anymore. n-api is included in every nodejs installation, and it's tiny. Directory walking has been improved massively with stream implementation of readdirp. Massive RAM & CPU improvements etc.

[ljharb]

I’m not sure why chokidar is a direct optional dep at all.

[polarathene]

@ljharb it was originally in the devDependencies prior to 1.0.0 it seems. But even then I don't see any usage of it. optionalDependencies is meant to be used for allowing a package to install correctly, even if an optional dependency fails to install(I'm guessing due to those fsevent errors/warnings?).

If it's really not needed for the package, then yeah, it probably should be removed..

[ljharb]

Right, but optionalDeps is part of the API of a package - there's no such thing as optional dev deps.