Create a repository for tasks made in GDScript that do not fit in LimboAI core, but may be useful for some projects

[limbonaut]

• Such tasks typically would be useful on a relatively small number of projects.
• Tasks in such a repository can be eventually promoted to core, if deemed worthy.
• Serves as an archive of examples for new users to learn from.
• Can be used for kick-starting future core tasks (experimental implementations).
• Can be put on Asset Lib, and imported partially - only bits you personally require.
• Platform for users to share their best bits.

[limbonaut]

Created a new public repo for additional BT tasks: https://github.com/limbonaut/limboai-extra

[smedelyan]

I think that maybe the following nodes better be in (or be added to) the core rather than reside there:

• PlayAudio / StopAudio
• GetAgentVar (gets some property from agent or specified object and puts it into blackboard)

Thoughts?

[limbonaut]

Blackboard variable binding interface is coming in the future (API already supports it in Blackboard.bind_var_to_property), so I opted for not adding GetAgentVar, as it will be obsolete when that support is added. The audio stuff may come to core, but tbh you can do the same using CallMethod. I don't want to go too granular with this, because Godot API is big - shouldn't make tasks for just about everything. It's trivial to add such tasks yourself, if you need them.