Accessibility

[soetz]

Describe the bug
I noticed a few accessibility issues while translating the docs to French (#63). They’re clearly not critical, but they’re still issues.

Here’s a list:

• There are a few jumps in heading levels, which is not very assistive technology-friendly. Example: https://axios-http.com/docs/urlencoded
• Related, I’m not 100% sure about this but I think having several consecutive headings without content in-between is an anti-pattern (a user using assistive technology would jump to the heading and expect there to be content). Example: https://axios-http.com/docs/api_intro
• From what I’ve seen, all clickable elements are keyboard-focusable, which is good, but the focus indicator is not always very visible, when there is any. At least on Firefox.
• The > text here Markdown blocks should probably translate to <aside> elements instead of <blockquote> because they are never used to indicate citations and aside is more semantic in this context.
• The text contrast is not WCAG-compliant for a lot of elements, though some of them seem ok to me in reality (the WCAG color contrast algorithm is not perfect (yet)).