*: Use tabs for indentation where appropriate

I am a big supporter of the approach to indent with tabs and align with
spaces. (Read [here][1] f.e.) Thus at some places a simple `s/ {4}/\t/g`
(replace 4 with whatever fits) is not enough and a bit more thought is
needed. Because of that there are still places where I plan to
substitute the whitespace in the future.

This patch contains exclusively whitespace changes. Check for yourself
with `git diff --ignore-all-space`.

[1]: https://dmitryfrank.com/articles/indent_with_tabs_align_with_spaces

.config/i3/airplane-mode-notify.sh

@@ -1,8 +1,8 @@
 #!/bin/sh
 
 if [ "$(rfkill -o SOFT --noheadings list wlan)" = "blocked" ]; then
-    notify-send "Airplane mode toggled" "On"
+	notify-send "Airplane mode toggled" "On"
 else
-    notify-send "Airplane mode toggled" "Off"
+	notify-send "Airplane mode toggled" "Off"
 fi