Make r<tab> and f<tab> work (helix-editor#4817)

Previously, commands such as `r<tab>` (replace with tab) or `t<tab>`
(select till tab) had no effect. This is because `KeyCode::Tab` needs
special treatment (like `KeyCode::Enter`).

helix-term/src/commands.rs

@@ -1131,6 +1131,10 @@ where
                 doc!(cx.editor).line_ending.as_str().chars().next().unwrap()
             }
 
+            KeyEvent {
+                code: KeyCode::Tab, ..
+            } => '\t',
+
             KeyEvent {
                 code: KeyCode::Char(ch),
                 ..
@@ -1277,6 +1281,9 @@ fn replace(cx: &mut Context) {
                 code: KeyCode::Enter,
                 ..
             } => Some(doc.line_ending.as_str()),
+            KeyEvent {
+                code: KeyCode::Tab, ..
+            } => Some("\t"),
             _ => None,
         };