eBird: report recent intergrade observations for region

[synrg]

Add intergrade observations to the [p]hybrids command.

• The API makes it seem as though you could specify cat=hybrid,intergrade, but that only returns hybrid results.
• It would be necessary, based on this test result, to do two searches, one for cat=hybrid, and another for cat=intergrade and combine the results.
• If the results are going to be mixed, it's probably not a good idea to drop (hybrid) from the name, which was thought to be redundant, but now would serve to distinguish those names from the intergrade results, which can have various parenthetical designations in their names, too.
• As well, it would be good to check with the eBird devs to see if cat=hybrid,intergrade ought to work and is broken, or if the docs can be improved to make it clear that only one category can be specified per query, as the way it is currently written (in the plural) makes it seem like it supports more than one.

[synrg]

See https://github.com/synrg/quaggagriff/issues/7#issuecomment-537476568 re help wanted.