Add Euforie theme from https://www.pling.com/p/1004842

There is no indication of the license for this theme, but since it is available on
Pling it is reasonable to assume it is free to use. Should the author
think this is not the case, please reach out to us and we will remove
the theme.

Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>

themes/CMakeLists.txt

@@ -1,6 +1,6 @@
 ##### default themes ################################
 
 install(
-    DIRECTORY Default-theme Bushido-Yellow-theme
+    DIRECTORY Default-theme Bushido-Yellow-theme Euforie-theme
     DESTINATION ${DATA_INSTALL_DIR}/deKorator/themes/
 )