Add %e in the terminal tab format tooltip.

Since it works, we may as well advertise it.

src/apps/terminal/TermConst.cpp

@@ -18,6 +18,7 @@ const char* const kTooTipSetTabTitlePlaceholders = B_TRANSLATE(
 	"\t\t\tOptionally the maximum number of path components can be\n"
 	"\t\t\tspecified. E.g. '%2d' for at most two components.\n"
 	"\t%i\t-\tThe index of the tab.\n"
+	"\t%e\t-\tThe encoding of the current tab. Not shown for UTF-8.\n"
 	"\t%p\t-\tThe name of the active process.\n"
 	"\t%%\t-\tThe character '%'.");