Update ts to allow allowImportingTsExtensions

[coxmi]

Hey,

Great project, but annoyingly it didn't work for me when importing ts extensions, like:

import { thing } from './file.ts'

tsconfig.json:

{
   "compilerOptions": {
      "allowImportingTsExtensions": true
   }
   ...
}

I've just upgraded the TS version to something more reasonable.