To use this in cmus, you'll need a single-binary build ("npm run build").
Make one and then place it anywhere you wish.
Then set it as your status displaying program. (Please check out the warning below.)
See https://github.com/weisslj/cmus_lastfm_autoadd/blob/78262fecb16c88828119eb6dfe7ecac09bf523a6/README for example.
WARNING:
CMUS invokes the program for any changes.
With the way cmus-discord-rpc works, more and more processes will be created as changes occur, eventually leading to OOMs.
A reference shell script ("cmus-discord-rpc" in the repo root) is my current solution to this.
It will attempt to pgrep for the executable's process and refuse to invoke it again if one is already running.
(On my machine, "cmus-discord-rpc-bin" is in PATH, so it works out of the box. Adjust paths & names if necessary.)
You can set it as the status display program instead of the executable.