Autogenerated documentation for supported VT sequences

[christianparpart]

Just like the terminfo file can be auto-generated, or the VT parser FSM,
it is also possible to auto-generate the list of supported VT sequences along with some additional info (might require adding more metadata but that's okay).

• expose list of supported VT sequences via CLI
• maybe support different formats? At least markdown? txt? man-page (groff)?

VT sequence meta data

• mnemonic
• VT syntax
• short description
• maybe a longer one?
• category tag(s) - such as "cursor placement", "rectangular"
• VT level or extension
• additional notes?

[Yaraslaut]

Closed by #1535