add legacy dinghy crate

[fredszaq]

already deployed on crates.io, this gives the following error message on install

 $ cargo install dinghy
    Updating crates.io index
  Downloaded dinghy v0.3.0
  Downloaded 1 crate (1.2 KB) in 0.97s
  Installing dinghy v0.3.0
   Compiling dinghy v0.3.0
error: failed to run custom build command for `dinghy v0.3.0`

Caused by:
  process didn't exit successfully: `/tmp/cargo-installgklDsG/release/build/dinghy-a36850d8e326f0b9/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at '



  The use of the dinghy crate is deprecated, use cargo-dinghy instead.

  Install it with the following command:

  	$ cargo install cargo-dinghy



      ', /home/fredszaq/.cargo/registry/src/github.heygears.com-1ecc6299db9ec823/dinghy-0.3.0/build.rs:2:5
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: failed to compile `dinghy v0.3.0`, intermediate artifacts can be found at `/tmp/cargo-installgklDsG`