This leads to code that is easier to understand and runs
faster thanks to GDScript's typed instructions.
The untyped declaration warning is now enabled on all projects
where type hints were added. All projects currently run without
any untyped declration warnings.
Dodge the Creeps and Squash the Creeps demos intentionally don't
use type hints to match the documentation, where type hints haven't
been adopted yet (given its beginner focus).
Opened them, saved all scenes, ran the project. Did necessary fixes here and there,
fixed some warnings (but some remain in bigger demos).
Did not port JRPG demo yet (#306) nor the two platformer demos.
