Feat: add contribution guidelines

[gefgu]

Fixes: #4

To add this contribution guidelines, I've used the contribution guidelines from the JavaScript Repo. Then, I changed the JavaScript-related things for TypeScript-related ones.

In the process, I've removed the test guidelines and some of the style guidelines because this project isn't fully set up yet. Also, I've used the TypeScript Standard Style in the style guide and hope it was the right decision.

Thanks for opportunity of working on this project :)

[raklaptudirm]

Add a little on using typescript's type system properly, like using any type is discouraged and so on.

[gefgu]

@raklaptudirm and @Panquesito7 thanks for the super awesome feedback. Already learned a lot with you both and added the semantic commit messages guidelines.

[appgurueu]

Another minor thing I noticed: You are inconsistent in your capitalization of lists. For (2?) lists you use

- foo.
- bar.
- baz.

and for the other ones you use

- Foo.
- Bar.
- Baz.

I'd recommend uppercasing the first letters of all list items, since these are separate sentences due to the periods separating them.

[raklaptudirm]

Left one comment, otherwise looks good to me.

[raklaptudirm]

LGTM