docs: add note about jest-axe (#226)

Author: skovy

README.md

@@ -866,6 +866,11 @@ independent from jest, and can be used with other tests runners as well.
 I'm not aware of any, if you are please [make a pull request][prs] and add it
 here!
 
+If you would like to further test the accessibility and validity of the DOM
+consider [`jest-axe`](https://github.com/nickcolley/jest-axe). It doesn't 
+overlap with `jest-dom` but can complement it for more in-depth accessibility 
+checking (eg: validating `aria` attributes or ensuring unique id attributes).
+
 ## Guiding Principles
 
 > [The more your tests resemble the way your software is used, the more