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/src/analyzer/SyntaxHelpers.ts

@@ -0,0 +1,80 @@
+// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
+// See LICENSE in the project root for license information.
+
+import * as ts from 'typescript';
+
+/**
+ * Helpers for validating various text string formats.
+ */
+export class SyntaxHelpers {
+	/**
+	 * Tests whether the input string is safe to use as an ECMAScript identifier without quotes.
+	 *
+	 * @remarks
+	 * For example:
+	 *
+	 * ```ts
+	 * class X {
+	 *   public okay: number = 1;
+	 *   public "not okay!": number = 2;
+	 * }
+	 * ```
+	 *
+	 * A precise check is extremely complicated and highly dependent on the ECMAScript standard version
+	 * and how faithfully the interpreter implements it.  To keep things simple, `isSafeUnquotedMemberIdentifier()`
+	 * conservatively accepts any identifier that would be valid with ECMAScript 5, and returns false otherwise.
+	 */
+	public static isSafeUnquotedMemberIdentifier(identifier: string): boolean {
+		if (identifier.length === 0) {
+			return false; // cannot be empty
+		}
+
+		if (!ts.isIdentifierStart(identifier.codePointAt(0)!, ts.ScriptTarget.ES5)) {
+			return false;
+		}
+
+		for (let index = 1; index < identifier.length; index++) {
+			if (!ts.isIdentifierPart(identifier.codePointAt(index)!, ts.ScriptTarget.ES5)) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	/**
+	 * Given an arbitrary input string, return a regular TypeScript identifier name.
+	 *
+	 * @remarks
+	 * Example input:  "api-extractor-lib1-test"
+	 * Example output: "apiExtractorLib1Test"
+	 */
+	public static makeCamelCaseIdentifier(input: string): string {
+		const parts: string[] = input.split(/\W+/).filter((x) => x.length > 0);
+		if (parts.length === 0) {
+			return '_';
+		}
+
+		for (let index = 0; index < parts.length; ++index) {
+			let part: string = parts[index]!;
+			if (part.toUpperCase() === part) {
+				// Preserve existing case unless the part is all upper-case
+				part = part.toLowerCase();
+			}
+
+			if (index === 0) {
+				// If the first part starts with a number, prepend "_"
+				if (/\d/.test(part.charAt(0))) {
+					part = '_' + part;
+				}
+			} else {
+				// Capitalize the first letter of each part, except for the first one
+				part = part.charAt(0).toUpperCase() + part.slice(1);
+			}
+
+			parts[index] = part;
+		}
+
+		return parts.join('');
+	}
+}