docs/rusticl: update opencl extensions and add rusticl to features.txt

Added a very small change to add cl_khr_create_command_queue which already exists in the code just not exposed

Todo:

• update extensions
• list supported? drivers (are any drivers really "supported")
• finish marking api spec
• figure out what drivers are supported on device dependent capabilities
• Should we remove the clover part? (prob not yet)
• get it working with https://mesamatrix.net/ depends on https://github.com/MightyCreak/mesamatrix/pull/270