docs: Document command to generate local html coverage report

[tpoliaw]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.09%. Comparing base (542153e) to head (1d7781f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1832   +/-   ##
=======================================
  Coverage   99.09%   99.09%           
=======================================
  Files         317      317           
  Lines       11991    11991           
=======================================
  Hits        11883    11883           
  Misses        108      108           

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[Villtord]

Not critically related to this change - do we have control over order of How-to pages? It feels like "checking coverage" should be close to "running tests" for me?

[tpoliaw]

It looks like it's alphabetical order with H1 sections promoted to full pages below their parent page (eg `Reusing an existing class follows Creating a new device because they're the same source file.

This is probably worthy of its own issue. The two example above probably shouldn't be listed as separate how-to guides.