Use TypeScript config and improve some types

[lukastaegert]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:

Description

To benefit from the new --configPlugin option, this will switch Rollup's own config to TypeScript. This immediately uncovered some inconsistencies in the typings that are resolved as well:

• The renderChunk hook is allowed to return undefined
• Plugins can also be falsy, in which case they are ignored

[github-actions]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#use-typescript-config

or load it into the REPL:
https://rollupjs.org/repl/?pr=4144

[codecov]

Codecov Report

Merging #4144 (37903aa) into master (bef5fe8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4144   +/-   ##
=======================================
  Coverage   98.28%   98.28%           
=======================================
  Files         201      201           
  Lines        7116     7116           
  Branches     2084     2084           
=======================================
  Hits         6994     6994           
  Misses         58       58           
  Partials       64       64           

Impacted Files	Coverage Δ
src/utils/ensureArray.ts	100.00% <ø> (ø)
src/utils/renderChunk.ts	100.00% <ø> (ø)

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