Add TypeScript support

[moshest]

Could be done by publishing definition file index.d.ts or by publishing a @types/stack-retrace package: https://github.com/DefinitelyTyped/DefinitelyTyped

[kobiburnley]

@moshest stack-retrace is already written in TypeScript and published with the declaration files.
We also recently added "types": "cjs/index.d.ts" in package.json

[moshest]

Cool!

If you can, export also the type RawSourceMap. Currently I had to require it via:

import { RawSourceMap } from 'stack-retrace/node_modules/source-map';

As this line throws me an error for mismatch type paths:

import { RawSourceMap } from 'source-map';