html: add parse_html

[fscherf]

This PR renames lona.html.parsing.html_string_to_node_list to lona.html.parse_html to make it official API that will replace HTML parsing in lona.html.HTML and lona.html.HTML2 (#268)

[SmithChart]

How does renaming make this an official API?
We probably want to add it to the documentation though :-)

Otherwise LGTM.

[fscherf]

How does renaming make this an official API?

lona.html.parsing.html_string_to_node_list was never meant to be documented, because the name is so clunky. Giving it a cleaner name and putting it into the documentation makes it "official" :)

[codecov-commenter]

Codecov Report

Patch coverage: 80.00% and project coverage change: -0.03 ⚠️

Comparison is base (d0b50b9) 71.30% compared to head (d2e6824) 71.27%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #436      +/-   ##
==========================================
- Coverage   71.30%   71.27%   -0.03%     
==========================================
  Files          83       83              
  Lines        5697     5699       +2     
  Branches     1226     1227       +1     
==========================================
  Hits         4062     4062              
- Misses       1345     1346       +1     
- Partials      290      291       +1     

Impacted Files	Coverage Δ
lona/html/parsing.py	87.50% <71.42%> (-1.17%)	⬇️
lona/html/__init__.py	100.00% <100.00%> (ø)
lona/html/widgets.py	62.50% <100.00%> (ø)

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[fscherf]

@SmithChart: I updated the documentation and all tests are green. I think in this state this is mergeable and closes #268

[SmithChart]

Thanks! Looks good.

[fscherf]

@SmithChart: \o/ Thanks for your review and your patience