upgrade typescript to 4.3

[43081j]

Fixes #214

This upgrades a bunch of dependencies:

• Upgraded typescript dependency to 4.3 such that we support newer syntax
• Added a .editorconfig - it looks like rune used tabs in most places so i went with that
• Updated the eslint plugins and eslint itself
• Updated ava
• Updated rollup, removed the old plugins and installed the scoped ones (@rollup/*)
• Replaced the ts rollup plugin with the official one
• Removed some ava typescript workaround rune had in there which seems to no longer be needed
• Upgrade lock file to v2

Added a test using override syntax too to ensure the syntax works.

cc @rictic @justinfagnani

[43081j]

no clue why that test fails in CI... if i re-introduce the extra spaces, it fails locally 🤔

edit: seems to build in ci at least with the spaces added back, seems like a potentially flaky test

[Niznikr]

@43081j Anything we can do to help move this along? This is the only blocker from our project upgrading to 4.3

[43081j]

i think we need @justinfagnani to review it and merge, its likely hes pretty busy with lit stuff right now though.

im happy with the change i think otherwise, seems to work well but could do with one thorough review