Add generated typescript definitions as part of build

[seleb]

Adds a new script build-types, which generates typescript definitions for the client class (using a similar pattern to build-rest).

Note: this is not comprehensive. Response types are only partially defined (they aren't in the existing json schema), and the plugins are not defined, but this still greatly improves the explorability and autocomplete of the API in a TS environment.

[seleb]

looks like the CI is failing, but only on node < 8, and it looks like master is red as well; is the legacy node support required?

[ebisbe]

The other day I was thinking that it would be a great improvement

[ebisbe]

@jeremyruppel is there any reason to having here doing nothing instead of shipping it?

After building it I see 2 missing parts:

// not comprehensive
type FlickrResponse = Promise<{
	body: any;
	ok: boolean;
}>;

and

// TODO: define static classes
	OAuth: any;
	Feeds: any;
	Upload: any;
	Replace: any;

[jeremyruppel]

@ebisbe thanks for the nudge, I'm ready to get this shipped. I'll fix those TODOs in main.

[ebisbe]

I did nothing. It's all thanks to @seleb !!

[jeremyruppel]

Yes of course! Amazing work @seleb!