fix(a11y): add main landmark, unique nav labels, and fix color contrast#7894

Rishabh037 wants to merge 3 commits intowebpack:mainwebpack/webpack.js.org:mainfrom

Rishabh037:fix/a11y-color-contrastRishabh037/webpack.js.org:fix/a11y-color-contrastCopy head branch name to clipboard