feat(options): add EZA_ICONS to environment variables

Signed-off-by: Sandro-Alessio Gierens <sandro@gierens.de>

src/options/vars.rs

@@ -26,6 +26,8 @@ pub static NO_COLOR: &str = "NO_COLOR";
 pub static EXA_COLORS: &str = "EXA_COLORS";
 pub static EZA_COLORS: &str = "EZA_COLORS";
 
+pub static EZA_ICONS: &str = "EZA_ICONS";
+
 /// Environment variable used to switch on strict argument checking, such as
 /// complaining if an argument was specified twice, or if two conflict.
 /// This is meant to be so you don’t accidentally introduce the wrong