Gracefully handle Ctrl-c and Escape

[ineu]

First of all I'd like to thank for the convenient tool to pick themes. There are some issues I've discovered:
1: The app incorrectly handles Ctrl-c:

1. Run alacritty-themes
2. Move to the next theme and quickly press Ctrl-c
   If the interrupt sequence is pressed fast enough, it catches the app in the middle of writing to alacritty.yml, leaving it half-written. The result is the broken config:
   

The app should trap C-c and finish the cleanup first

2: The app incorrectly handles Esc:

1. Run alacritty-themes
2. Move to a theme
3. Press Esc
   Expected: the selection process aborts, leaving the previous theme
   Actual: a theme under cursor is applied like if Enter was pressed.

[JuanVqz]

@rajasegar what do you think about adding a hacktoberfest label? it could help many people know about alacritty-themes.

[rajasegar]

Sounds good to me

[rajasegar]

@JuanVqz Added the label to the repo as well

[JuanVqz]

you already did it, thank you, what else can we add with the hacktoberfest label? BTW I'm about to add a contributors section in the readme, are you agree?

[rajasegar]

Yes 👍