Update locale option list

siunitx.tex

@@ -3253,9 +3253,9 @@ \subsection{Locale options}
 \pkg{siunitx} allows the user to switch between the typographic conventions of
 different (geographical) areas by using locales. Currently, the package is
 supplied with configurations for locales \opt{UK}, \opt{US}, \opt{DE}
-(Germany), \opt{PL} (Poland), \opt{FR} (French), \opt{SI} (Slovene) and \opt{ZA} (South Africa).
-The \opt{locale}
-option is used to switch to a particular locale.
+(Germany), \opt{IT} (Italian) \opt{PL} (Poland), \opt{FR} (French), \opt{SI}
+(Slovene) and \opt{ZA} (South Africa). The \opt{locale} option is used to
+switch to a particular locale.
 \begin{LaTeXdemo}
   \qty{1.234}{\metre}\\
   \qty[locale = DE]{6.789}{\metre}