Proton: enable dxvk d3d9 support by default

[soredake]

Feature Request

I confirm:

• [X] that I haven't found another request for this feature.
• [X] that I have checked whether there are updates for my system available that
  contain this feature already.

Description

Enable d3d9 from dxvk, it is mature enough already, hundreds of games will benefit from this.

Justification [optional]

Risks [optional]

References [optional]

[shoober420]

I support this change as well.

[kisak-valve]

Closing as implemented per "Direct3D 9 games will now use DXVK for rendering by default. Users without Vulkan support can return to the OpenGL-based wined3d renderer with the PROTON_USE_WINED3D configuration option." in Proton 5.0-1.

[soredake]

Thanks!