feat: Initial clean release of CHM

packages/editor/polyfills.ts

@@ -0,0 +1,45 @@
+
+//
+// JSDOM and browser polyfills:
+//
+// If running in JSDOM, a number of visual browser APIs are missing
+// or incomplete.
+// This file may also be included when running in a browser. As such, the methods
+// should be added only if missing.
+//
+
+const createMockRect = (): DOMRect => {
+	const rect = {
+		width: 1,
+		height: 2,
+		left: 3,
+		top: 4,
+		bottom: 5,
+		right: 6,
+		x: 3,
+		y: 4,
+	};
+
+	return {
+		...rect,
+		toJSON: () => JSON.stringify(rect),
+	};
+};
+HTMLElement.prototype.getBoundingClientRect ??= () => {
+	return createMockRect();
+};
+
+// Prevents the CodeMirror error "getClientRects is undefined".
+// See https://github.com/jsdom/jsdom/issues/3002#issue-652790925
+Range.prototype.getBoundingClientRect ??= () => {
+	return createMockRect();
+};
+
+Range.prototype.getClientRects ??= () => {
+	return {
+		length: 0,
+		item: () => null,
+		[Symbol.iterator]: () => null,
+	};
+};
+