new rule: react-a11y-anchors

[HamletDRC]

Link text should be as least four 4 characters long. (http://oaa-accessibility.org/wcag20/rule/38/)

Links with the same HREF should have the same link text. (http://oaa-accessibility.org/wcag20/rule/39/)

Links that point to different HREFs should have different link text. (http://oaa-accessibility.org/wcag20/rule/41/)

Links with images and text content, the alt attribute should be unique to the text content or empty. (http://oaa-accessibility.org/wcag20/rule/43/)

Enforce an anchor element's href prop value is not just #.

• http://webaim.org/techniques/hypertext/#keyboard