fix(html): preserve code blocks in list items (#2131)

* chore(html): refactor parser to leverage context managers

Signed-off-by: Cesar Berrospi Ramis <ceb@zurich.ibm.com>

* fix(html): parse inline code snippets, also from list items

Signed-off-by: Cesar Berrospi Ramis <ceb@zurich.ibm.com>

* chore(html): remove hidden tags

Remove tags that are not meant to be displayed.
Add regression tests for code blocks, inline code, and hidden tags.

Signed-off-by: Cesar Berrospi Ramis <ceb@zurich.ibm.com>

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Signed-off-by: Cesar Berrospi Ramis <ceb@zurich.ibm.com>