feat: add auto update support

src/cli/help.ts

@@ -17,6 +17,7 @@ ${B}Session${R}
   --stats                        Open the stats dashboard in your browser
   --texthooker                   Start texthooker server only ${D}(no overlay)${R}
   --open-browser                 Open texthooker in your default browser
+  --update                       Check for updates
 
 ${B}Overlay${R}
   --toggle-visible-overlay       Toggle subtitle overlay