Added Spinner widget (#3871)

docs/reference/src/language/widgets/index.rst

@@ -24,6 +24,7 @@ Widgets
    scrollview.md
    slider.md
    spinbox.md
+   spinner.md
    standardbutton.md
    standardlistview.md
    standardtableview.md

docs/reference/src/language/widgets/spinner.md

@@ -0,0 +1,24 @@
+<!-- Copyright © SixtyFPS GmbH <info@slint.dev> ; SPDX-License-Identifier: MIT -->
+
+## `Spinner`
+
+The `Spinner` informs the user about the status of an on-going operation, such as loading data from the network. It provides the same properties as
+[`ProgressIndicator`](./progressindicator.md) but differs in shape.
+
+### Properties
+
+-   **`indeterminate`**: (_in_ _bool_): Set to true if the progress of the operation cannot be determined by value (default value: `false`).
+-   **`progress`** (_in_ _float_): Percentage of completion, as value between 0 and 1. Values less than 0 or greater than 1 are capped.
+
+### Example
+
+```slint
+import { Spinner } from "std-widgets.slint";
+export component Example inherits Window {
+    width: 200px;
+    height: 25px;
+    Spinner {
+        progress: 50%;
+    }
+}
+```