docs: Update output and add HTML output as an option in the output.md doc.

[another-rex]

Several small changes:

• Update the output doc to include HTML output
• Update Feedback link to point to the correct feedback discussion
• Clarify the error logging message to warn people to update osv-scanner if base image scanning fails.
• Actually fail base image scanning to avoid spamming people with the log.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 69.17%. Comparing base (3ee976e) to head (a5766db).

Files with missing lines	Patch %	Lines
...ts/clientimpl/baseimagematcher/baseimagematcher.go	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1541      +/-   ##
==========================================
- Coverage   69.18%   69.17%   -0.02%     
==========================================
  Files         200      200              
  Lines       18988    18989       +1     
==========================================
- Hits        13137    13135       -2     
- Misses       5141     5143       +2     
- Partials      710      711       +1     

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