Begin custom shader drawing.
Note
This function has been auto-generated from the following Raylib function definition:
void BeginShaderMode(Shader shader);See also
shader() for creating shader objects.
Other shader functions: 
end_shader_mode(),
get_shader_location_attrib(),
get_shader_location(),
load_shader_from_memory(),
load_shader(),
set_shader_value_matrix(),
set_shader_value_texture(),
set_shader_value(),
unload_shader()
Other mode functions: 
begin_blend_mode(),
begin_mode_2d(),
begin_mode_3d(),
begin_scissor_mode(),
begin_texture_mode(),
end_blend_mode(),
end_mode_2d(),
end_mode_3d(),
end_scissor_mode(),
end_shader_mode(),
end_texture_mode(),
end_vr_stereo_mode(),
set_camera_mode()
