Feat: interpolate colors (#208)

* feat: interpolate theme colors

* doc: add interpolated colors to readme

utils/interpolate_utils.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+do_color_interpolation() {
+	local all_interpolated="$1"
+
+	for ((i=0; i<${#color_interpolation[@]}; i++)); do
+		all_interpolated=${all_interpolated//${color_interpolation[$i]}/${color_values[$i]}}
+	done
+
+	echo "$all_interpolated"
+}