Document `app.bind`

[Klustre]

Premiere supports binding callback functions to interface events through

app.bind(eventName, func)

This script uses the following events. Not sure if this is an exhaustive list (@bbb999?)

app.bind("onSourceClipSelectedInProjectPanel", func)
app.bind("onItemsAddedToProjectSuccess", func)
app.bind("onProjectChanged", func)
app.bind("onActiveSequenceStructureChanged", func)
app.bind("onActiveSequenceChanged", func)
app.bind("onActiveSequenceSelectionChanged", func)
app.bind("onSequenceActivated", func)
app.bind("onActiveSequenceTrackItemRemoved", func)
app.bind("onActiveSequenceTrackItemAdded", func)
app.bind("onActiveSequenceStructureChanged", func)