heffalump conduit and installer

hotsync conduit for Heffalump (palmOS mastadon client)

installation

this crate exports two build targets:

1. the heffalump_conduit library, which produces heffalump_conduit.dll
2. the heffalump_conduit_install executable, which produces heffalump_conduit_install.exe

to install the conduit:

1. replace the environment variables in .cargo/config with the relevant tokens
2. build both targets with cargo build --release
3. copy heffalump_conduit.dll to the same folder as the hotsync executable
4. run heffalump_conduit_install.exe