Add documentation build and badge

[mjul]

Add Cljdoc link and badge to README to make API documentation easily accessible.

See Cljdoc for details on how to set this up.

https://github.com/cljdoc/cljdoc/blob/master/doc/userguide/for-library-authors.adoc#basic-setup

[EleekaN]

Hi @mjul , I think I can do this.
Under which section in readme, you want the link and the badge added?

[mjul]

@EleekaN That's great, just place it where you think it is most relevant. Maybe before the examples in the Usage section?

Also, when you send a pull request, don't forget to add your name to the contributor list in the README file.

Thanks again.

[EleekaN]

Thank you @mjul for this opportunity.