Add includesText() alias

[Oreoz]

Fixes #30.

I did not find tests for other aliases, therefore I didn't write any for this one.

I edited the API.md file manually (EditorConfig had some fun) in order to add mention of the alias. I wasn't sure if it was generated or maintained manually.

[Turbo87]

I edited the API.md file manually (EditorConfig had some fun) in order to add mention of the alias. I wasn't sure if it was generated or maintained manually.

you can yarn run docs and it will automatically generate the API.md file :)

[Oreoz]

There you go! Generated the docs using yarn run docs.

I also took the liberty of adding a minuscule 'Contributing' section in the README to cover stuff I tripped up on. I hope that's alright with you.

[Turbo87]

awesome, thanks!!

[Turbo87]

if you want to continue working on this I was thinking that maybe another alias containsText() might also be good, and then we should probably make includesText() the main implementation (due to String.prototype.includes()) and hasTextContaining() an alias to includesText().

[Oreoz]

Sure thing, if I have some spare time today, I'll look into that!