Rename demo folder to project for generalizing the template usecase

Renames all references to the demo folder and changes it to "project"

project/project.godot

@@ -0,0 +1,15 @@
+; Engine configuration file.
+; It's best edited using the editor UI and not directly,
+; since the parameters that go here are not all obvious.
+;
+; Format:
+;   [section] ; section goes between []
+;   param=value ; assign values to parameters
+
+config_version=5
+
+[application]
+
+config/name="godot cpp template"
+config/features=PackedStringArray("4.1", "Forward Plus")
+config/icon="res://icon.svg"