add parsing for GLTF COLOR_0

[redcamel]

add parsing for GLTF COLOR_0.

[redcamel]

vec4 COLOR_0은 처리되었고..
vec3 COLOR_0은 테스트후 추가해야함
현재상황 - test link

[cx20]

I confimed that it has been fixed and updated the status of the Vertex Color model in gltf-test.

[redcamel]

@cx20 resolved of COLOR_0 alpha blend.
test at this link.

[cx20]

@redcamel Thank you for fixing it. I confirmed the fix.
RedGL + PrimaryIonDrive.glb result:

[redcamel]

vec3은 샘플 예제를 하나 찾은후 추후반영하는걸로.