Allow keywords for features #36
Description
Recognize a new property named keywords of a feature, as a YAML string array.
This allows features to contain hidden information that is not necessarily available in their titles.
For example, Expansion Statements (template for) does not have "Reflection" in its title, although in practice its use might also be related to C++26 Reflection.
When a user is searching for the term "reflection", it would be helpful to also list the Expansion Statements feature in the search results.
Recognizing keywords generally allows the categorization of features, but could also clutter search results with unrelated features. Therefore, the keywords of a feature should be sparse and specific.