Generate configuration documentation

[Yaraslaut]

It is often quite easy to forget about documentation entry on the web-page when adding new entry to the configuration.
Some parts of the web-page are generated using contour executable already, for example info about supported VT sequences (https://contour-terminal.org/vt-sequence/) and key mapping section (https://contour-terminal.org/configuration/key-mapping/)
It would be great to provide automatic generation of config entries for the web-page

Automatic generation:

• global config
• profile config
• key mapping
• we can ignore the color scheme because changes are rare