feat: added typescript support and definitions + some validation

[KarolNov]

In order to test out if I can use this repo as boilerplate for my purpose I played around with adding TS + some basic validation. This PR contains results of my work.

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[samuelkraft]

Hi @KarolNov, thanks for the PR! Sorry for the slow response here, I've been debating whether adding typescript is a good idea or not for this repo due to added complexity for beginners. I want to keep the repo accessible to new devs and that was the main reason it was not added in the beginning. After giving it some thought I think the benefits outweighs the potential complexity. Would you mind solving the outstanding conflict so I can merge this? Thanks

[KarolNov]

@samuelkraft I guess that make sense and the typings I did are quite complicated (I use different built-in magic methods like Extract) and might be confusing for beginners. I wonder what's the best solution here, but I'm planning to build an open source CMS engine for Notion using Typescript, so I guess once that's published anyone interested in Typescript version can go and find it. If you still think it's worth it I can resolve the conflict when I'll have some spare time.

[samuelkraft]

Closing this to focus on the basic js implementation