Check navbar color contrast

[MartijnCuppens]

The color contrast on the dark navbar doesn't seem to meet the minimum contrast ratio:
https://contrast-ratio.com/#rgba%28255%2C255%2C255%2C.5%29-on-%23343a40

[XhmikosR]

We should really tackle #29315 :) Regardless, check out the Node.js 12 action; it now has the HTML results uploaded