Closes#1405
- Properly uses `typescript-eslint`: we were missing the preset from it,
so some of the default `eslint` rules (that don't properly work with
typescript) were being applied and causing false positives
- I also moved the `eslint` config into its own file, and enabled
`typescript-eslint`'s type-awareness, so that we can enable more
type-aware rules in the future if we like
- Adds `ts-lit-plugin` to the typescript config, which _hopefully_ will
allow us to catch issues during build (in CI)
- It looks like `ts-lit-plugin` is sort of abandonware at the moment,
and unfortunately _doesn't_ actually work for this purpose right now,
but the lit team is working on a replacement here:
https://www.npmjs.com/package/@lit-labs/analyzer
- Adds `fork-ts-checker-webpack-plugin`, which allows the typescript
checking process to be run on a separate forked thread in Webpack, which
can help speed up builds & checking
- Enables incremental type checking for better speed
- Fixes a whole bunch of `eslint`-auto-fixable issues (unused imports
and variables, some type issues, etc)
- Fixes a bunch of `lit-analyzer` issues (mostly attribute naming, some
type issues as well)
- Fixes various other type issues:
- Improves type safety in a bunch of places, notably anywhere `apiFetch`
and `APIPaginatedList` are used
- Removes some `any`s
