[fix][doc] Fix broken doc links in historical versions prior to 2.8.0

[momo-jun]

Fix #17688 and #16701

Modifications

Fix broken doc links in historical versions prior to 2.8.0 by adding .md.

This is an automatic search and replacement with only a couple of manual adjustments.

• Regex: (\[[^\]]+\]\((?!http|assets|\.|\/|#)((?!\.md|:|\.|#|\/).)*)\)
• Replacement: $1.md)

Documentation

• [x] doc