code: function addExtensionsToContext(gl) {
    for (let ii = 0; ii < supportedExtensions.length; ++ii) {
      addExtensionToContext(gl, supportedExtensions[ii]);
    }
  }
docs: 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 existance 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