[ty] Render reStructuredText hyperlinks in docstring Markdown

[lerebear]

Summary

Closes astral-sh/ty#3529.

Test Plan

Please see included tests.

[codspeed-hq]

Merging this PR will not alter performance

✅ 67 untouched benchmarks
⏩ 60 skipped benchmarks¹

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_{Comparing lerebear/push-nvtwqlqkyktm (f0f9b7c) with lerebear/push-usmovrotyxzm (cba0858)}

Footnotes

1. 60 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩