Include colons for typable commands in command palette (#4495)

Before:

    Goto next buffer. [buffer-next]

After:

    Goto next buffer. [:buffer-next]

helix-term/src/commands.rs

@@ -2443,8 +2443,8 @@ impl ui::menu::Item for MappableCommand {
 
         match self {
             MappableCommand::Typable { doc, name, .. } => match keymap.get(name as &String) {
-                Some(bindings) => format!("{} ({}) [{}]", doc, fmt_binding(bindings), name).into(),
+                Some(bindings) => format!("{} ({}) [:{}]", doc, fmt_binding(bindings), name).into(),
-                None => format!("{} [{}]", doc, name).into(),
+                None => format!("{} [:{}]", doc, name).into(),
             },
             MappableCommand::Static { doc, name, .. } => match keymap.get(*name) {
                 Some(bindings) => format!("{} ({}) [{}]", doc, fmt_binding(bindings), name).into(),