function addExtensionsToContext(gl) {
  for (var ii = 0; ii < supportedExtensions.length; ++ii) {
    addExtensionToContext(gl, supportedExtensions[ii]);
  }
}
Attempts to enable all of the following extensions
and add their functions and constants to the
`WebGLRenderingContext` using their normal non-extension like names.

     ANGLE_instanced_arrays
     EXT_blend_minmax
     EXT_color_buffer_float
     EXT_color_buffer_half_float
     EXT_disjoint_timer_query
     EXT_disjoint_timer_query_webgl2
     EXT_frag_depth
     EXT_sRGB
     EXT_shader_texture_lod
     EXT_texture_filter_anisotropic
     OES_element_index_uint
     OES_standard_derivatives
     OES_texture_float
     OES_texture_float_linear
     OES_texture_half_float
     OES_texture_half_float_linear
     OES_vertex_array_object
     WEBGL_color_buffer_float
     WEBGL_compressed_texture_atc
     WEBGL_compressed_texture_etc1
     WEBGL_compressed_texture_pvrtc
     WEBGL_compressed_texture_s3tc
     WEBGL_compressed_texture_s3tc_srgb
     WEBGL_depth_texture
     WEBGL_draw_buffers

For example if `ANGLE_instanced_arrays` exists then the functions
`drawArraysInstanced`, `drawElementsInstanced`, `vertexAttribDivisor`
and the constant `VERTEX_ATTRIB_ARRAY_DIVISOR` are added to the
`WebGLRenderingContext`.

Note that if you want to know if the extension exists you should
probably call `gl.getExtension` for each extension. Alternatively
you can check for the existence of the functions or constants that
are expected to be added. For example

   if (gl.drawBuffers) {
     // Either WEBGL_draw_buffers was enabled OR you're running in WebGL2
     ....

@param {WebGLRenderingContext} gl A WebGLRenderingContext
@memberOf module:twgl