typescript re-write

[mmkal]

Fixes #56

This replaces coffee/omelette.coffee with typescript/omelette.ts

Some notes:

• The implementation aims to match the runtime output as closely as possible to src/omelette.js, rather than trying to match the coffee source to typescript
• It aims to match the type definition output to the existing definitelytyped module: https://github.com/DefinitelyTyped/DefinitelyTyped/blob/26b0538e9b3cd7498827609a59c09eb5a2fdd58b/types/omelette/index.d.ts
• Neither of the above was possible to match 100%, so some help testing would be appreciated! I didn't change .travis.yml, I haven't used it in a few years, not sure some extra bits are needed
• added typescript as a dev dependency
• Which also required using a package manager to install (I used pnpm but can switch to npm or yarn if preferred)
• Which also required adding a .gitignore containing node_modules and a pnpm-lock.yaml
• added a tsconfig.json (strict is enabled though this required using one non-null assertion (this.word!)
• added a build script to package.json
• added the types field to package.json
• added a test/test-d.ts file to make sure the types don't regress, copying from https://github.com/DefinitelyTyped/DefinitelyTyped/blob/26b0538e9b3cd7498827609a59c09eb5a2fdd58b/types/omelette/omelette-tests.ts
• added a test script to package.json which currently just compiles the types test file

Stuff I didn't change:

• any CI workflows (I noticed there are both github actions and travis)
• didn't remove the src/omelette.js folder, even though it's generated from typescript/omelette.ts - keeping under source control is somewhat unconventional but it's equivalent to how it was with Coffeescript
• didn't aim to improve any implementations or type definitions along the way - thought there'd be more value in a port that matches the published version as closely as possible
• any consolidation with deno
• any file/folder organization patterns. It's somewhat unusual to have the compiled output live in src/, usually that would be for the "source" code (typescript/coffee), and the output would be in dist/ or lib/. But not a big deal so I left it.

Any/all of those could come after, but I don't see them as problems per se - esp if updates to this repo aren't too frequent and releases are manual.

Review notes:

• it might be better to look at the diff to src/omelette.js rather than typescript/omelette.ts (you'll need to "show large diffs" and will want to ignore whitespace changes if viewing on github)

Testing:

• autocompletion is obviously v hard to test on a CI runner, but I tried it out by linking locally to my trpc-cli which uses omelette to add completions to a CLI built from a trpc router (commander instance under the hood). Types and runtime look good, but again help testing would be great!