[Docs] Add keypoints order images in zh_cn doc

[walsvid]

Motivation

Added description of keypoints for datasets supported by mmpose.

Modification

Add visualization of keypoints order for datasets supported by mmpose, including 2D/3D hands, 2D/3D human bodies, fullbody, animal, etc.
Update keypoints order to the Chinese document.

BC-breaking (Optional)

Use cases (Optional)

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit tests to ensure correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.