Fix Earewien#10 : compatibility with Godot 4 beta 13+ : annotation sh…

…ould be placed before extend keyword

Fix Earewien#9 : BTBlackboard hold weak references to nodes (and only…

… nodes)

Fix Earewien#8 : BTActionCallable expression result can be an int, no…

…t a BTTickResult !

Centralize expression evaluation into BTExpression object. delta vari…

…able is now accessible into expressions

Prepare next release

Fix Earewien#3 : Custom performance monitor in BTRoot produces erros …

…when node is removed from tree

Fix Earewien#1 : StringName cannot be concatenate to Strings before G…

…odot 4 beta 10

Use a safer way to concatenate values to string litterals

Update README to add exemple of custom nodes and a brief description …

…about behavior trees