Adds aria described by to tooltip plugin for accessibility

Generates a unique id for tooltip and adds [aria-describedby] to the element
it is called on. Resolves issue #13480

- set up test
- linted the code styles
- passed the tests
- integrated feedback from @cvrebert
Merge pull request #13557 from bassettsj/aria-describedby-tooltip-13480

Aria describedby tooltip: #13480