**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
return ui::VKEY_NUMPAD0;
  } else if (str == "num1") {
    return ui::VKEY_NUMPAD1;
  } else if (str == "num2") {
    return ui::VKEY_NUMPAD2;
  } else if (str == "num3") {
    return ui::VKEY_NUMPAD3;
  } else if (str == "num4") {
    return ui::VKEY_NUMPAD4;
  } else if (str == "num5") {
    return ui::VKEY_NUMPAD5;
  } else if (str == "num6") {
    return ui::VKEY_NUMPAD6;
  } else if (str == "num7") {
    return ui::VKEY_NUMPAD7;
  } else if (str == "num8") {
    return ui::VKEY_NUMPAD8;
  } else if (str == "num9") {
    return ui::VKEY_NUMPAD9;
  } else if (str == "numadd") {
    return ui::VKEY_ADD;
  } else if (str == "nummult") {
    return ui::VKEY_MULTIPLY;
  } else if (str == "numdec") {
    return ui::VKEY_DECIMAL;
  } else if (str == "numsub") {
    return ui::VKEY_SUBTRACT;
  } else if (str == "numdiv") {
    return ui::VKEY_DIVIDE;
  } else if (str == "space") {