[examples] Add bone blending animation example

[dmitrii-brand]

• Demonstrates per-bone animation blending for smooth transitions
• Supports upper/lower body selective blending (walk + attack)
• Includes uniform blending mode for comparison
• Uses GPU skinning for performance
• Follows raylib example conventions

[raysan5]

@dmitrii-brand Note that there is another similar example here: #4578, how does it compare?

[dmitrii-brand]

@dmitrii-brand Note that there is another similar example here: #4578, how does it compare?

This is just an example, it does not make any changes to lib itself.

[raysan5]

Note that the header section does not follow required structure, there is no Copyright line, it should be added or it will fail on processing.

[raysan5]

@dmitrii-brand Please, could you rename the example to just models_animation_blending? Also a screenshot needs to be provided, you can capture automatically it from running example with F12.

Also added a comment for review about the header information, copyright data is required, check other examples for reference.

[dmitrii-brand]

Thanks will do

[raysan5]

@dmitrii-brand I'm merging the example, I will review the missing bits. Thanks for the addition.