Find a Wormhole Executable
Value
The absolute path to the wormhole executable as a character string.
Attribute version-string comprises the wormhole --version output,
and attributes name and version the parsed version string.
If no executable exists, an error is produced.
Details
Unless R option future.p2p.wormhole specifies an executable, the default
is to download and install wormhole-william locally and use that one.