Add target for changing track send pan

[Benjamin Klum]

A note about track send mute: Track send mute is not that important because it can be simulated by changing track send volume. Additionally, REAPER doesn't notify extensions if track send mute has changed, so learning track send mute or feedback would not be possible for that.

[Benjamin Klum]

re #86 Add target "Track send pan"

→ <<cset 4a2c53c1f407>>