workspace: Add NewFileSplit action with direction (#39726)

Add new `workspace::NewFileSplit` action which expects a
`SplitDirection` argument, allowing users to programmatically control
the direction of the split in keymaps, for example:

```json
{
    "context": "Editor",
    "bindings": {
        "ctrl-s ctrl-h": ["workspace::NewFileSplit", "left"],
        "ctrl-s ctrl-j": ["workspace::NewFileSplit", "down"],
        "ctrl-s ctrl-k": ["workspace::NewFileSplit", "up"],
        "ctrl-s ctrl-l": ["workspace::NewFileSplit", "right"]
    }
}
```

Release Notes:

- Added `workspace::NewFileSplit` action, which can be used to
programmatically split the editor in the provided direction.

Co-authored-by: Rian Drake <rian.drake@rocketwerkz.com>
Co-authored-by: dino <dinojoaocosta@gmail.com>

crates/workspace/src/workspace.rs

@@ -302,6 +302,12 @@ pub struct MoveItemToPaneInDirection {
     pub clone: bool,
 }
 
+/// Creates a new file in a split of the desired direction.
+#[derive(Clone, Deserialize, PartialEq, JsonSchema, Action)]
+#[action(namespace = workspace)]
+#[serde(deny_unknown_fields)]
+pub struct NewFileSplit(pub SplitDirection);
+
 fn default_right() -> SplitDirection {
     SplitDirection::Right
 }