tiny-typed-emitter should be (production) dependencies

[jesec]

Otherwise TS projects that depends on feedsub need to add tiny-typed-emitter to their devDependencies. That messes up the dependency chain.

Additionally, FeedItem type should be (re)exported via export {FeedItem} from 'feedme';.

[fent]

hi, thanks for the feedback. this change was just pushed, i wasn't sure about putting tiny-typed-emitter in either dependencies or devDependencies. but now i see that compiled code in dist/feedsub.js does reference it. i don't know why i didn't think to check, so thanks for letting me know.