Fix Alt+Shift+Char for crossterm backend

Before this patch `cargo run --example key_codes --features crossterm-backend`:

    AltChar('e')
    Char('E')

After:

    AltChar('e')
    AltChar('E')

Author: azat

cursive/src/backends/crossterm.rs

@@ -101,6 +101,11 @@ fn translate_event(event: CKeyEvent) -> Option<Event> {
                 code: KeyCode::Char(c),
                 ..
             } => Event::AltChar(c),
+            CKeyEvent {
+                modifiers: ALT_SHIFT,
+                code: KeyCode::Char(c),
+                ..
+            } => Event::AltChar(c),
             CKeyEvent {
                 modifiers: KeyModifiers::SHIFT,
                 code: KeyCode::Char(c),