Typescript tasks

[charlierudolph]

Now that we have converted to Typescript have a few post merge tasks that would be nice:

• tsconfig - set noImplicitAny to true (build: add noImplicitAny and noImplicitReturns, fix compilation #1286)
• tsconfig - set noImplicitThis to true (typescript: noImplicitThis #1283)
• tsconfig - set noImplicitReturns to true (build: add noImplicitAny and noImplicitReturns, fix compilation #1286)
• checkout using https://api-extractor.com/ - better to wait until after [api-extractor] Support "import * as __ from __" for local paths microsoft/rushstack#1029 is fixed
• add changelog entry noting the rewrite to TypeScript (docs: add changelog note about typescript #1414)
• remove external typings in DefinitelyTyped after release ([cucumber] remove typings, package now ships its own DefinitelyTyped/DefinitelyTyped#47104)

Please comment if you think there are other tasks we should complete and I can add them to the list. Also comment if you start working on a task

[davidjgoss]

Picking up the api-extractor thing if no one objects - won't be short but shouldn't conflict with any of the others.

Also think it might be good to put some guards in with https://www.npmjs.com/package/tsd so we test the typings against typical usages in support code and custom formatters.

[davidjgoss]

Update from me - had a go with api-extractor but ran into a corner case issue where re-exporting the Status enum from cucumber-messages trips it up. I've gotten some help from the rushstack team and will dig in a little more this week.

Also I am picking up noImplicitReturns and noImplicitAny now

cc @charlierudolph

[davidjgoss]

Draft PR raised for DefinitelyTyped DefinitelyTyped/DefinitelyTyped#47104 - will be mergeable once we release 7.0.0