feat: toggle Cerebro search from the command line

• I am on the latest Cerebro.app version

• I have searched the issues of this repo and believe that this is not a duplicate

• OS version and name: Linux Mint 19.04

• Cerebro.app version: Latest Release

Issue

I would like to know if it's possible at all to toggle cerebro using the command line? e.g. with something like

$ cerebro toggle

This would be wonderful, because I prefer to use Super+Space as my launch command (immitating Spotlight on OSX). However, on Linux Mint 19.04 you have to hit space twice before Cerebro will "catch" the command. I've experienced this issue before with apps that try to use global hotkeys and the work-around is to create a custom system-wide shortcut; but to do that you need a terminal command that can be invoked by the shortcut.