feat!: enable show source links

[machow]

This PR adds a show source link to rendered item docs. Addresses #354

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 77.63158% with 17 lines in your changes missing coverage. Please review.

Project coverage is 88.18%. Comparing base (4739a4e) to head (8a18dbd).

Files with missing lines	Patch %	Lines
quartodoc/repo_info.py	78.04%	9 Missing ⚠️
quartodoc/renderers/md_renderer.py	60.00%	6 Missing ⚠️
quartodoc/autosummary.py	60.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #363      +/-   ##
==========================================
- Coverage   88.46%   88.18%   -0.29%     
==========================================
  Files          37       39       +2     
  Lines        2931     3005      +74     
==========================================
+ Hits         2593     2650      +57     
- Misses        338      355      +17     

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