Upgrade ESLint & TypeScript ESLint Plugins

[bigtimebuddy]

FINALLY, after all those PRs, we can now upgrade ESLint. This PR fixes a few more tiny issues and add some linting exceptions where necessary.

In general, this newer version of ESLint + plugins is much stricter and works better parsing with the latest TypeScript version. We still have a few any types that should get fixed eventually, but this is a big, much needed upgrade.

Everything still runs: https://pixijs.io/examples/?v=dev-typescript-linting#/demos-basic/container.js

[codecov-commenter]

Codecov Report

Merging #6710 into dev will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               dev     #6710   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           15        15           
  Lines          671       671           
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  Hits           671       671           

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[cursedcoder]

Looks OK

[themoonrat]

Everything looks fine - my only comment is here @bigtimebuddy . Why would a function be docced as private, yet not be private in typescript?

[bigtimebuddy]

There’s not really a concept of internal in TypeScript but if there was, this would be it. We’ve made things public even though they are only referenced externally (eg _tingRGB). This function is overridden by the unsafe-eval package so to keep from throwing a linting error it’s easier to make it public even if it never shows up in the docs. I think there’s a way we can exclude stuff like this from typings when we get there.

In summary: this is non-public API, but used by another package.