Recognize `tag_invoke` as idiomatic

[akrzemi1]

tag_invoke is a C++ idiom proposed in P1895.
It became popular and used in libraries:

• Boost.JSON: https://www.boost.org/doc/libs/1_86_0/boost/json/value_to.hpp
• P2300 (but ultimately abandoned): https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2300r10.html#design-dispatch
• NWGraph: https://github.com/pnnl/NWGraph/blob/master/include/nwgraph/volos.hpp#L130
• libunifex: https://github.com/facebookexperimental/libunifex/blob/main/include/unifex/then.hpp#L105
• HPX: https://github.com/TheHPXProject/hpx/blob/master/libs/core/executors/include/hpx/executors/execute_on.hpp#L128

MrDocs should recognize it, and at minimum, when listing tag_invoke, also provide its first tag parameter, as otherwise sole tag_invoke missies the point: https://develop.capy.cpp.al/capy/reference/boost/capy/const_buffer.html#_friends

[vinniefalco]

The correct way to implement this is through scripted addons that recognize the idiom and rewrite the Corpus.