docs: add webmaster instructions the single-file html

[joanise]

PR Goal?

Give webmasters a blunt message that the single-file HTML format is not intended for publication as is.

Feedback sought?

review the text

Priority?

normal

Tests added?

not needed

How to test?

readalongs align -l fra tests/data/ej-fra.txt tests/data/ej-fra.m4a delme
less delme/Offline-HTML/delme.html

and see the webmaster webmaster warning and then the webmaster instructions.

Confidence?

high

Version change?

no

Related PR

ReadAlongs/Studio-Web#554

[semanticdiff-com]

Review changes with  

Changed Files

File	Status
readalongs/text/make_package.py	28% smaller

[github-actions]

CLI load time: 0:00.04
Pull Request HEAD: 3a4455037843f4a23ae65783cbb71863d06b602f
No imports take more than 0.1 s.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.76%. Comparing base (17ceaa3) to head (3a44550).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #305   +/-   ##
=======================================
  Coverage   93.76%   93.76%           
=======================================
  Files          21       21           
  Lines        1765     1765           
  Branches      295      295           
=======================================
  Hits         1655     1655           
  Misses         73       73           
  Partials       37       37           

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