feat: support eslint v9

[Jungzl]

fix: #92

[robatwilliams]

Hi. Thanks for your effort on this. As it's a significant piece of work which we hadn't already discussed, I need some understanding of the changes made and why.

As I see:

• Dropped Node 16 support
• Upgraded lerna
• Upgraded various other packages (run all, prettier, browserslist ...)
• Changed from npm to pnpm
• No tests against ESLint 8
• ...

Could you elaborate please?

Is it all necessary just to support 9, or is it bundling together some good-to-do general maintenance in the same PR?

[Jungzl]

Sorry for submitting many changes at once. I believe including excessive irrelevant code solely to accommodate ESLint 9 is somewhat bothersome. It might be better to divide it into several pull requests.
Anyway, I can explain the reasons for these changes to you.

Dropped Node 16 support

Node16 LTS is EOL in September 11th, 2023;
ESLint no longer supports versions below node 18.18;

Upgraded lerna

To be honest, I just upgraded all the dependencies that could be upgraded. I saw #77 before, since lerna actively maintained recently, let's give it a try.

Upgraded various other packages (run all, prettier, browserslist ...)

I replaced eslint-plugin-import with eslint-plugin-import-x, the latter is a rewrite of the former with TS and legacy node support dropped.
I replaced npm-run-all with npm-run-all2, it has documented its advantages.

Changed from npm to pnpm

pnpm is more suitable for this monorepo, reduce lock files and shadow dependencies

And I didn't test it on ESLint 8 since it's a breaking change, so users who use ESLint 8 should continue to use version 3.2.1.