Update repo structure

[baseten]

Part of: https://github.com/play-co/react-pixi/issues/10

Probably easiest to review commit by commit, sorry I should have separated the last commit between the ESLint fixes and the test fixes, hiding whitespace might help

Changes

• Update node version
• Update all deps to latest versions
• Convert repo structure to match assetpack
• Update rollup config and remove UMD
• Apply PIXI linting rules to everything
• Fix tests to work with Jest modern timers