**Is your feature request related to a problem? Please describe.**
The Caps Lock and Fn keys are useful to some, and not others. I would greatly enjoy being able to use these keys as modifiers for something more useful to me.

**Describe the solution you'd like**
Add global shortcuts support for the cap locks and fn keys. While these keys are not useless and are not proper modifier keys, I feel that the design choice should be left to the app developer.

**Describe alternatives you've considered**
The only alternative would be to use a keypress listener/sender to 'remap' the key to something Electron supports; or substitute electron's shortcut functionality completely.

**Additional context**
Using a 3rd party keypress listener does not feel safe.
atom/common/keyboard_util.cc
case 'v':
      return ui::VKEY_V;
    case 'w':
      return ui::VKEY_W;
    case 'x':
      return ui::VKEY_X;
    case 'y':
      return ui::VKEY_Y;
    case 'z':
      return ui::VKEY_Z;
    case ')':
      *shifted = true;
      FALLTHROUGH;
    case '0':
      return ui::VKEY_0;
    case '!':
      *shifted = true;
      FALLTHROUGH;
    case '1':
      return ui::VKEY_1;
    case '@':
      *shifted = true;
      FALLTHROUGH;
    case '2':
      return ui::VKEY_2;
    case '#':
      *shifted = true;
      FALLTHROUGH;
    case '3':
      return ui::VKEY_3;