Add Skeleton modifier design article

[TokageItLab]

SkeletonModifier3D was implemented by godotengine/godot#87888 with some Skeleton processes reworking. This article is intended to help community users understand the modification process and enable them to develop custom IK, physical bone and etc.

• Closes There is no PhysicalBone3D/SkeletonModifier3D migration document godot#94831

[TokageItLab]

I added a tutorial about creating a custom SkeletonModifier3D. Note that it depends on the following two PRs. So those must be merged before publishing this article.

• Expose get_skeleton() from SkeletonModifier3D godot#92896
• Add get_concatenated_bone_names() to Skeleton3D for SkeletonModifier3D's enum hints godot#92925

[TokageItLab]

@clayjohn @coppolaemilio May I request proofreading for publication?

[clayjohn]

I will try to review this shortly!

[adamscott]

As we're using .webp for serving images, we should use .webm for serving videos.

[TokageItLab]

@adamscott I think webm may not play on some apple devices (iOS). Besides, we still use mp4 in our recent articles (such as godot-4-2-beta release article).

[Calinou]

I think webm may not play on some apple devices (iOS)

Both VP8 and VP9 WebM are supported since iOS 17.4: https://caniuse.com/webm
Other browsers (including macOS Safari) have had WebM support for a much longer time.

godot-docs have started to use it, e.g. on Prototyping levels with CSG.

VP9 is more efficient than H.264, so we should use it to save on bandwidth.

[TokageItLab]

Replaced.

[adamscott]

Besides, we still use mp4 in our recent articles (such as godot-4-2-beta release article).

😰

[Calinou]

Besides, we still use mp4 in our recent articles (such as godot-4-2-beta release article).

😰

We can (and should) keep using H.264 on existing pages, as converting the videos from a lossy format to another will further decrease quality with no gains in efficiency. We don't have lossless sources for those videos that we could re-encode in VP9.

[clayjohn]

Great work! I just did an English language pass to help clarify things.

I did not review the images or code in depth

[TokageItLab]

@clayjohn Thank you very much! I have looked at each of the proposals, and I believe it is very fine, as no change of intent has been made.

[clayjohn]

The text looks good to me, I haven't reviewed the images but I am sure they are great

[coppolaemilio]

Thank you so much!