Migration: html2print -> html2pdf4doc

[stanislaw]

To avoid collisions with numerous PyPI and NPM packages and to better emphasize the purpose of the project we decided to rename the project as follows:

• html2pdf4doc (Pip)
• HTML2PDF4Doc (full name)

The rest of the migration will be performed gradually with separate PRs:

• Create the Pip package. Migration: html2print -> html2pdf4doc #38
• Rename Python files. Migration: html2print -> html2pdf4doc #38
• Rename everything in the Python code. Migration: html2print -> html2pdf4doc #38
• When the parent JS repo is also renamed, update to the new upstream. chore(.gitmodules): update to the rename submodule: html2pdf -> html2pdf4doc #74
• Rename the Python repo.
• Update StrictDoc's dependency.
• Retire the html2print after some time, remove it from PyPI (>6 months from now).