Grab release, place component .dll in \foobar2000\components\ or create foo_drpc directory in %userdir%\AppData\Roaming\foobar2000\user-components\ and drop component .dll in there.
Grab release from https://github.com/discordapp/discord-rpc and place the discord-rpc.dll from the \bin\ directory in your foobar200 root directory (alongside foobar2000.exe).
Add foobar2000 to discords detected games (Settings -> Games -> Add it).

How to compile

Compiled with VS 2017.
Grab foobar2000 SDK and create \foo_drpc\ directory in \foobar2000.
Drop contents from repository in the prevoiusly created \foo_drpc.
Grab release from https://github.com/discordapp/discord-rpc and place \lib\ with contained discord-rpc.lib in \foo_drpc.
Do the same with \include\discord-rpc.h but this time directly into \foo_drpc.
Get/Create a Discord Application ID which resembles your App at Discords end and fill in to \Plugin.h.
Upload 1 large asset for your App with the key "logo", 3 small ones with keys "play", "stop" and "pause".

License and Warranty

Check LICENSE. Note: Even though I build in a "spam protection" to avoid lots of presence updates being send to the discord servers, I can't guarantee and am not responsible for any actions that may be taken against your account. (Nothing happened during personal testing)