Fix for PC Line Renderer shader returns color in wrong Color Space

[RTAzis]

The Line Renderer/Gradient(?) returns a color property always in Gamma space, but Linear space is recommended and mostly used in VRChat, so it should be converted if Linear space is configured in the project settings. Otherwise the colors are faded and not as bright as they should be and as configured by the user.

An example of the issue with #8441A1 color:

QVPen Color Gradient settings:

Without fix #BE8AD0:

With fix #8441A1:

[RTAzis]

@ureishi このプルリクエストを確認するために時間をかけてください。