[doc/book] add RQL use cases with search/card/python/javascript
Related to https://www.cubicweb.org/ticket/3899077
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')