Initializes support for Web MIDI Link.
Once created, the handler listens for postMessage events from the parent window.
When it receives a MIDI message in the format "midi,xx,yy,zz" (hex bytes), it forwards it to the synthesizer.
The synthesizer instance to connect the link to.
This class adds Web MIDI Link support to the synthesizer.
Web MIDI Link allows other web pages (for example, online MIDI editors) to control the synthesizer by sending MIDI messages to its window.