Some Quality of Life Fixes

[avivbeeri]

I loved the design and aesthetic of this tool from the moment I ran it, but I spotted some opportunities for improvement:

• I've made ESC as an alias for the 'q' command to quit, as well as for exiting the "Shift+S" mode.
• Until this PR, you could click anywhere and change random tiles due to modulo calculations. It now checks if your mouse is actually hovering inside the range of the tile before showing a cursor or making changes.
• The .gitignore file wasn't excluding the built binary for me, so I corrected that.

[DaKnig]

I don't like the bit about ESC for exiting the app- it's not something you find commonly in tui apps in the Unix world- see ESC in man, less, emacs, vi etc. the rest are fine additions.

[avivbeeri]

I use vim heavily, so I guess I'm just used to do ESC being a part of the overall "quit" process.
Happy to change it if desired.

It's a nice key for "cancel" in certain dialogs and stuff though, so its use could be expanded there.

[avivbeeri]

To clarify, the ESC key in this PR doesn't actually "quit" the program, but it does bring up the prompt to quit, which doesn't seem too unreasonable. You can always press it again to ignore the prompt and go back to editing.