Allows opacity to be set via main menu or keyboard shortcuts[correct one]

[akash-joshi]

What does this PR do?
I made the menu described in #84 . It allows opacity to be changed via the menu or Keyboard shortcuts.

Showing working via keyboard shortcuts :

Apologies about the previous PR, it didn't have the correct file pushed in it.

What platforms did you test it on?
OSX, Windows 7

[alxwrd]

Just a thought, you could do something like this?

{
  label: 'Set Opacity',
  submenu: (() => {
      var result = []
      let level = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].forEach((num) => {
          result.push({
              label: `${num}0%`,
              accelerator: `CmdOrCtrl+${num}`,
              click() {
                  mainWindow.webContents.send('opacity.sync', num * 10);
                  mainWindow.setOpacity(num / 10.0);
              }
          })
      })
      return result
  })()
}

[akash-joshi]

@alxwrd Incorporated your suggestion. Just changed forEach to a map function and put a check for CmdOrCtrl+0

[kamranahmedse]

Thanks guys