Improve docs: A11y: Link vs text contrast does not meet WCAG guidelines

[mobot11]

Description

WCAG requires "A 3:1 contrast between the link text color and the surrounding non-link text color." This might turn into an issue with fiori-fundamentals. Can check the allowable contrast levels here: https://webaim.org/resources/linkcontrastchecker/

Versions

fundamental-react:
fiori-fundamentals:

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[bcullman]

@mobot11 3:1 contrast ratio is reserved for exceptionally large text. For the majority of the text, we actually need to hit 4.5:1.

[droshev]

@mobot11 is this specifically to fundamental-react or it comes from fiori-fundamentals?

[mobot11]

@droshev Looks like these are the defaults from fiori-fundamentals. I can open an issue on that repo as well.

[jbadan]

@mobot11 @droshev A couple of the buttons have this same problem, specifically medium (orange) and light buttons.

Edit: The light buttons only fail with our code sample background which will be fixed by #461

[mobot11]

@bcullman I believe specifically for the contrast between the link color and the text color we are only required to provide a 3:1 ratio according to https://webaim.org/articles/contrast/#only.

[gszalay]

The short version: I don't see any problems.

I reviewed the Fundamental Link (https://sap.github.io/fundamental/components/link.html) page and had 2 quick findings:

1. The colors in Fundamental do not match the colors in the Fiori 3 Master Sketch file. I would therefore assume the Fundamental colors are not final and will change.
2. This section of WebAim (https://webaim.org/articles/contrast/#only) applies to links when no other indicator (such as underline) is used. So, the 3:1 rule is not applicable if there is an underline (which is displayed in Fundamental)