Move uncritical files into etc/ (#350)

This is mainly just to reduce the amount of files in the project root.
The criteria of what gets into `etc/` are the following:

* The file should not be necessary for building nsxiv. This excludes the
  `icon/*` stuff since that's needed by `window.c`.
* The file shouldn't have any valid reason to stay in the project root.
  This excludes things like `README.md`, `.gitignore` etc.

Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/350
Reviewed-by: explosion-mental <explosion-mental@noreply.codeberg.org>

etc/examples/image-info

@@ -0,0 +1,21 @@
+#!/bin/sh
+
+# Example for $XDG_CONFIG_HOME/nsxiv/exec/image-info
+# Called by nsxiv(1) whenever an image gets loaded.
+# The output is displayed in nsxiv's status bar.
+# Arguments:
+#   $1: path to image file (as provided by the user)
+#   $2: image width
+#   $3: image height
+#   $4: fully resolved path to the image file
+
+s="  " # field separator
+
+exec 2>/dev/null
+
+filename=$(basename -- "$1")
+filesize=$(du -Hh -- "$1" | cut -f 1)
+geometry="${2}x${3}"
+
+echo "${filesize}${s}${geometry}${s}${filename}"
+