DOC: Add pages for undocumented subcommands

[Lucas-C]

Currently in docs/user/ we only have 3 subcommands over 11 existing ones.

PRs are welcome to add dedicated documentation pages for the remaining subcommands,
taking inspiration from the existing ones:

• https://pdfly.readthedocs.io/en/latest/user/subcommand-cat.html
• https://pdfly.readthedocs.io/en/latest/user/subcommand-meta.html
• https://pdfly.readthedocs.io/en/latest/user/subcommand-x2pdf.html

[moormaster]

I also added some PRs for documenting

• extract-annotated-pages command - DOC: add documentation for extract-annotated-pages subcommand #157
• and rotate command - DOC: add documentation for rotate subcommand #158

[Lucas-C]

Thank you 👍