Tried to clarify segment filters in documentation. Made example not use deprecated matchers.

[xax]

Tried to improve clarity of segment definition and filters. Made example not use deprecated matchers and use shorter glob pattern.

[jmooring]

Thanks for this. Some of what you provided isn't quite right, and surfaced a bug while testing. I will keep this open for a while, and will likely replace it with a separate PR once we've addressed the underlying issue. This was a useful exercise.

[xax]

Updated guessing correct usage in analogy to documentation regarding content management » front matter :: Target.

sites
: {{< new-in 0.153.0 />}}
: (`map`) A map to define [sites matrix](g).

is an "difficult" explanation, I think, as while sites being technically a map (in this understanding), that map does hold nothing but the "matrix" map, which is the map defining the "matrix" axes. A lot of boilerplate to write – but granted: it is consistent.