Add an input field to enter commands

When the user presses `escape` or `CTRL + c`, show an input field at the bottom of the screen that gets input, just like vim's. Close if one of the buttons to show it is pressed again. If enter is pressed, try to run the command and show an error message where the input is if the command errors out or doesn't exist. No commands need to be implemented yet, just make a working input field.