wezterm: normalize configured keys

To avoid confusing behavior, normalize the configured keys
in the same way that we normalize key presses.

In other words, this:

```lua
{
  key = "y",
  mods = "CTRL|SHIFT",
  action = "Copy",
}
```

is treated as if you wrote:

```lua
{
  key = "Y",
  mods = "CTRL",
  action = "Copy",
}
```

refs: https://github.com/wez/wezterm/issues/372

config/src/lib.rs

@@ -992,7 +992,8 @@ impl Config {
         let mut map = HashMap::new();
 
         for k in &self.keys {
-            map.insert((k.key.clone(), k.mods), k.action.clone());
+            let (key, mods) = k.key.normalize_shift(k.mods);
+            map.insert((key, mods), k.action.clone());
         }
 
         Ok(map)