Add note about inertia being required for apply_torque on various Node types

[compmstr]

see: #68068

Bugsquad edit:

• Fixes apply_torque on RigidBody2D does not work if bodys CollisionShape2D is disabled #68068

[Calinou]

The same note is likely relevant for RigidBody3D and PhysicsDirectBodyState3D. Can you check there?

[compmstr]

Checked in the code, and calculating angular velocity uses _inv_inertia_tensor, so it appears that inertia is required for 3D as well. Added a similar note to apply_torque functions for RigidBody3D

[mhilbrunner]

Please squash the commits into one :)

[compmstr]

I think that commit squashing is done upon merging? Or am I missing an option in Github?

[Zireael07]

@compmstr: It can be done upon merging, but Godot engine repo doesn't use this option

[compmstr]

I followed https://docs.godotengine.org/en/stable/community/contributing/pr_workflow.html#the-interactive-rebase, and I think I've got it set up correctly. TIL about manually squashing commits, thank you :)

I also added the note to PhysicsDirectBodyState3D.

[compmstr]

I fixed the CI issues:

• had to change 'param' to 'member' for the inertia members
• I had the class reference tags wrong (it's just [ClassName] instead of [class ClassName])

[akien-mga]

We only use one space after a period in the docs. (Same for all added sentences.)

[akien-mga]

Note that the email associated with your Git identity for this commit is not valid (see https://github.com/godotengine/godot/pull/68098.patch). It's not a problem per se but it means the commit can't be attributed to your GitHub account. If you want to fix that, you should change your Git identity locally and amend the commit with git commit --amend --reset-author.
https://docs.github.com/en/account-and-profile/setting-up-and-managing-your-personal-account-on-github/managing-email-preferences/setting-your-commit-email-address#setting-your-commit-email-address-in-git

[compmstr]

Thanks for the note about the email address. I fixed that, and the double spaces after periods.

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉