[EUI+] Fix all broken links

[weronikaolejniczak]

The purpose of this task is to go through all the pages and fix all broken links.

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Known cases:

• props tables anchor links (e.g. EuiHeader props table: #EuiHeaderSection, #EuiBreadcrumbResponsiveMaxCount) are broken - clicking these items should scroll the user to the prop table section on the page,
• links to other docs pages appear to be broken (example, EuiMarkdownEditor and EuiMarkdownFormat links in first sentence),
• All links on the homepage appear to be broken and there’s a minified React error in DevTools.

Update this list as you work on the ticket to aid in the QA.