Add runOnConnect hook triggered only by actual source connection

[nosideg]

Describe the feature

Currently, hooks such as runOnInit or others tied to path availability are also triggered when alwaysAvailable is enabled, even though no source is actually connected. This makes it impossible to run scripts or actions only when a genuine incoming stream becomes active.

Please add a new hook—like runOnConnect—that is triggered only when a real source begins streaming to a path.

[aler9]

suggestion for the parameter name: runOnOnline since the names we've started to use are:

• "available" to refer to streams that are linked to either an online publisher or an offline always-available video
• "online" to refer to streams that are linked to an online publisher