[FL-3925, FL-3942, FL-3944] JS features & bugfixes (SDK 0.2) (#4075)

* feat: JS GPIO PWM, JS GUI Widget view; fix: JS EvtLoop stop on request, JS EvtLoop stop on error
* fix: f18 build
* docs: widget
* fix: js unit test
* change feature naming

Co-authored-by: あく <alleteam@gmail.com>

applications/system/js_app/packages/fz-sdk/gui/widget.d.ts

@@ -0,0 +1,66 @@
+/**
+ * Displays a combination of custom elements on one screen.
+ * 
+ * <img src="../images/widget.png" width="200" alt="Sample screenshot of the view" />
+ * 
+ * ```js
+ * let eventLoop = require("event_loop");
+ * let gui = require("gui");
+ * let emptyView = require("gui/widget");
+ * ```
+ * 
+ * This module depends on the `gui` module, which in turn depends on the
+ * `event_loop` module, so they _must_ be imported in this order. It is also
+ * recommended to conceptualize these modules first before using this one.
+ * 
+ * # Example
+ * For an example refer to the GUI example.
+ * 
+ * # View props
+ * This view does not have any props.
+ * 
+ * # Children
+ * This view has the elements as its children.
+ * 
+ * @version Added in JS SDK 0.2, extra feature `"gui-widget"`
+ * @module
+ */
+
+import type { View, ViewFactory } from ".";
+import type { IconData } from "./icon";
+import type { Contract } from "../event_loop";
+
+type Position = { x: number, y: number };
+type Size = { w: number, h: number };
+type Alignment = { align: `${"t" | "c" | "b"}${"l" | "m" | "r"}` };
+type Font = { font: "primary" | "secondary" | "keyboard" | "big_numbers" };
+type Text = { text: string };
+
+type StringMultilineElement = { element: "string_multiline" } & Position & Alignment & Font & Text;
+type StringElement = { element: "string" } & Position & Alignment & Font & Text;
+type TextBoxElement = { element: "text_box", stripToDots: boolean } & Position & Size & Alignment & Text;
+type TextScrollElement = { element: "text_scroll" } & Position & Size & Text;
+type ButtonElement = { element: "button", button: "left" | "center" | "right" } & Text;
+type IconElement = { element: "icon", iconData: IconData } & Position;
+type FrameElement = { element: "frame", radius: number } & Position & Size;
+
+type Element = StringMultilineElement
+    | StringElement
+    | TextBoxElement
+    | TextScrollElement
+    | ButtonElement
+    | IconElement
+    | FrameElement;
+
+type Props = {};
+type Child = Element;
+declare class Widget extends View<Props, Child> {
+    /**
+     * Event source for buttons. Only gets fired if there's a corresponding
+     * button element.
+     */
+    button: Contract<"left" | "center" | "right">;
+}
+declare class WidgetFactory extends ViewFactory<Props, Child, Widget> { }
+declare const factory: WidgetFactory;
+export = factory;