Declaration files

[edqd]

Hello again :)
current build configuration does not produce declaration files for typescript and on usage the typescript server seems to load index.ts file instead of package.main which produces plenty TS errors such as:
ERROR in /<redacted>/node_modules/deep-state-observer/index.ts(168,17): TS7009: 'new' expression, whose target lacks a construct signature, implicitly has an 'any' type.
rollup-plugin-typescript is know to have problems with emitting declaration files..
Can, you please look at this? I can also try to put up a pull request if you're open to it :)
Thanks for your great work 👍