osmo-adsb-gen/gr-adsbtx/docs

This is the adsbtx-write-a-block package meant as a guide to building
out-of-tree packages. To use the adsbtx blocks, the Python namespaces
is in 'adsbtx', which is imported as:

    import adsbtx

See the Doxygen documentation for details about the blocks available
in this package. A quick listing of the details can be found in Python
after importing by using:

    help(adsbtx)