Support `-e` flag at startup

Is your feature request related to a problem? Please describe.
I previously have been using tdrop to help provide a drop-down terminal in combination with KDE's konsole. However, tdrop requires a -e flag to setup the terminal correctly. hyper simply opens another window when I try to execute it with tdrop due to missing this option.
This would also be useful more generally to immediately execute a command in a new terminal window.

Describe the solution you'd like
Add a -e flag that has the same behaviour as konsole, xterm, and many other terminal emulators.

Describe alternatives you've considered
It looks like there are a couple of NPM modules that implement drop-down behaviour, eg. hyper-overlay, but all that I can find support only MacOS and don't work in Linux.

Additional context
I've never worked on an Electron project before, but I'd be willing to investigate implementing this feature if the idea is acceptable. At a guess I could build on top of the shell options that are already supported by .hyper.js

Start by tracing Hyper's startup argument handling and the existing shell options in .hyper.js. Compare the requested -e behavior with the linked Konsole and xterm conventions, then verify that launching Hyper with a command opens one terminal window and executes that command.