/**
 * Traverses all `props.children` to obtain their combined textual content.
 *
 * This function does not add spaces for readability:
 * `<p>Hello <em>world</em>!</p>` produces `Hello world!` as expected,
 * but `<p>Hello</p><p>world</p>` returns `Helloworld`, similar to
 * the behavior of https://mdn.io/Node/textContent.
 *
 * @param {ReactElement} elem - The React element from which to extract textual content. Can be a React element, string, number, or boolean.
 * @param {string} [childContentSeparator=""] - A string used to separate the child values. Defaults to an empty string.
 *
 * @returns {string} A combined string containing the textual content of the provided React element's children.
 *
 * @example
 * const element = (
 *   <div>
 *     <p>Hello <em>world</em>!</p>
 *     <p>How are you?</p>
 *   </div>
 * );
 *
 * const textContent = getTextContent(element, ' '); // Returns "Hello world! How are you?"
 */
export default function getTextContent(elem: any, childContentSeparator?: string): string;