Updated kdbx file icon

* Tweaked share/icons/svg/application-x-keepassxc.svg for better scaling
* Added ico build script for Windows

share/windows/create-ico.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+if [[ -z "$1" ]]; then
+  echo "You must include an SVG file to convert!"
+  exit 1
+fi
+
+outfile=$2
+if [[ -z "outfile" ]]; then
+  outfile="logo.ico"
+fi
+
+echo "Generating $outfile from $1..."
+size_list=(16 24 32 48 64 128 256)
+for size in ${size_list[@]}; do
+    inkscape -z -e $size.png -w $size -h $size "$1" >/dev/null 2>/dev/null
+done
+
+images=`printf "%s.png " "${size_list[@]}"`
+convert $images $outfile
+
+rm $images