style: Improve eslint setup

[robbie-c]

Problem

Just code style

Changes

Added eslint-plugin-react-hooks, eslint-plugin-jest, and eslint:recommended.

Then manually went through and fixed anything that needed fixing. I spent a bit of time thinking through the react hooks changes, to convince myself that they were correct/beneficial, and a reviewer probably would want to do the same.

Release info Sub-libraries affected

Bump level

• Major
• Minor
• Patch

Libraries affected

• All of them
• posthog-web
• posthog-node
• posthog-react-native

Changelog notes

• Added eslint plugins (eslint-plugin-react-hooks and eslint-plugin-jest) and config (eslint:recommended)

[neilkakkar]

Not sure about the posthog provider changes, was this prompted by some eslint rule?

But otherwise LGTM!

[robbie-c]

Yeah, it comes from eslint-plugin-react-hooks, a plugin made by the react team (https://www.npmjs.com/package/eslint-plugin-react-hooks)