Add documentation about fastclick
Made a small change to fastclick docs
Add a part about how to disable fastclick for an element
Typo
Document the fastclick package

Summary: Add a section about fastclick to the packages part of the docs

Test Plan: It's just a docs change

Reviewers: slava

Reviewed By: slava

CC: nim

Differential Revision: https://phabricator.meteor.com/D821