Configure alacritty

- add config file ~/.config/alacritty/alacritty.yml
  (not synced by mackup)
- make Gnome's <Super>t shortcut start a new alacritty instance
- fix minor mouse issue interacting with vim

.config/gnome-settings/key-bindings.ini

@@ -97,13 +97,13 @@ name='Google Chrome'
 [org/gnome/settings-daemon/plugins/media-keys/custom-keybindings/custom5]
 # Mimic i3wm's default way to open terminals
 binding='<Super>Return'
-command='gnome-terminal'
+command='alacritty'
 name='Terminal (1)'
 
 [org/gnome/settings-daemon/plugins/media-keys/custom-keybindings/custom6]
 # Faster than the default <Primary><Alt>t
 binding='<Super>t'
-command='gnome-terminal'
+command='alacritty'
 name='Terminal (2)'
 
 [org/gnome/settings-daemon/plugins/media-keys/custom-keybindings/custom7]