build: package api-extractor and -model (#9920)

* fix(ExceptText): don't display import("d..-types/v10"). in return type

* Squashed 'packages/api-extractor-model/' content from commit 39ecb196c

git-subtree-dir: packages/api-extractor-model
git-subtree-split: 39ecb196ca210bdf84ba6c9cadb1bb93571849d7

* Squashed 'packages/api-extractor/' content from commit 341ad6c51

git-subtree-dir: packages/api-extractor
git-subtree-split: 341ad6c51b01656d4f73b74ad4bdb3095f9262c4

* feat(api-extractor): add api-extractor and -model

* fix: package.json docs script

* fix(SourcLink): use <> instead of function syntax

* fix: make packages private

* fix: rest params showing in docs, added labels

* fix: missed two files

* fix: cpy-cli & pnpm-lock

* fix: increase icon size

* fix: icon size again

packages/api-extractor-model/src/mixins/ApiReadonlyMixin.ts

@@ -0,0 +1,137 @@
+// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
+// See LICENSE in the project root for license information.
+
+import type { ApiItem, IApiItemJson, IApiItemConstructor, IApiItemOptions } from '../items/ApiItem.js';
+import type { DeserializerContext } from '../model/DeserializerContext.js';
+
+/**
+ * Constructor options for {@link (ApiReadonlyMixin:interface)}.
+ *
+ * @public
+ */
+export interface IApiReadonlyMixinOptions extends IApiItemOptions {
+	isReadonly: boolean;
+}
+
+export interface IApiReadonlyMixinJson extends IApiItemJson {
+	isReadonly: boolean;
+}
+
+const _isReadonly: unique symbol = Symbol('ApiReadonlyMixin._isReadonly');
+
+/**
+ * The mixin base class for API items that cannot be modified after instantiation.
+ * Examples such as the readonly modifier and only having a getter but no setter.
+ *
+ * @remarks
+ *
+ * This is part of the {@link ApiModel} hierarchy of classes, which are serializable representations of
+ * API declarations.  The non-abstract classes (e.g. `ApiClass`, `ApiEnum`, `ApiInterface`, etc.) use
+ * TypeScript "mixin" functions (e.g. `ApiDeclaredItem`, `ApiItemContainerMixin`, etc.) to add various
+ * features that cannot be represented as a normal inheritance chain (since TypeScript does not allow a child class
+ * to extend more than one base class).  The "mixin" is a TypeScript merged declaration with three components:
+ * the function that generates a subclass, an interface that describes the members of the subclass, and
+ * a namespace containing static members of the class.
+ * @public
+ */
+
+export interface ApiReadonlyMixin extends ApiItem {
+	/**
+	 * Indicates that the API item's value cannot be assigned by an external consumer.
+	 *
+	 * @remarks
+	 * Examples of API items that would be considered "read only" by API Extractor:
+	 *
+	 * - A class or interface's property that has the `readonly` modifier.
+	 *
+	 * - A variable that has the `const` modifier.
+	 *
+	 * - A property or variable whose TSDoc comment includes the `@readonly` tag.
+	 *
+	 * - A property declaration with a getter but no setter.
+	 *
+	 * Note that if the `readonly` keyword appears in a type annotation, this does not
+	 * guarantee that that the API item will be considered readonly. For example:
+	 *
+	 * ```ts
+	 * declare class C {
+	 *   // isReadonly=false in this case, because C.x is assignable
+	 *   public x: readonly string[];
+	 * }
+	 * ```
+	 */
+	readonly isReadonly: boolean;
+
+	serializeInto(jsonObject: Partial<IApiItemJson>): void;
+}
+
+/**
+ * Mixin function for {@link (ApiReadonlyMixin:interface)}.
+ *
+ * @param baseClass - The base class to be extended
+ * @returns A child class that extends baseClass, adding the {@link (ApiReadonlyMixin:interface)}
+ * functionality.
+ * @public
+ */
+export function ApiReadonlyMixin<TBaseClass extends IApiItemConstructor>(
+	baseClass: TBaseClass,
+): TBaseClass & (new (...args: any[]) => ApiReadonlyMixin) {
+	class MixedClass extends baseClass implements ApiReadonlyMixin {
+		public [_isReadonly]: boolean;
+
+		public constructor(...args: any[]) {
+			super(...args);
+
+			const options: IApiReadonlyMixinOptions = args[0];
+			this[_isReadonly] = options.isReadonly;
+		}
+
+		/**
+		 * @override
+		 */
+		public static override onDeserializeInto(
+			options: Partial<IApiReadonlyMixinOptions>,
+			context: DeserializerContext,
+			jsonObject: IApiReadonlyMixinJson,
+		): void {
+			baseClass.onDeserializeInto(options, context, jsonObject);
+
+			options.isReadonly = jsonObject.isReadonly || false;
+		}
+
+		public get isReadonly(): boolean {
+			return this[_isReadonly];
+		}
+
+		/**
+		 * @override
+		 */
+		public override serializeInto(jsonObject: Partial<IApiReadonlyMixinJson>): void {
+			super.serializeInto(jsonObject);
+
+			jsonObject.isReadonly = this.isReadonly;
+		}
+	}
+
+	return MixedClass;
+}
+
+/**
+ * Static members for {@link (ApiReadonlyMixin:interface)}.
+ *
+ * @public
+ */
+export namespace ApiReadonlyMixin {
+	/**
+	 * A type guard that tests whether the specified `ApiItem` subclass extends the `ApiReadonlyMixin` mixin.
+	 *
+	 * @remarks
+	 *
+	 * The JavaScript `instanceof` operator cannot be used to test for mixin inheritance, because each invocation of
+	 * the mixin function produces a different subclass.  (This could be mitigated by `Symbol.hasInstance`, however
+	 * the TypeScript type system cannot invoke a runtime test.)
+	 */
+	export function isBaseClassOf(apiItem: ApiItem): apiItem is ApiReadonlyMixin {
+		return apiItem.hasOwnProperty(_isReadonly);
+	}
+}