/**
 * Deeply merges two objects. The `source` object properties will overwrite the `target` object properties.
 * If a property value is an object, it will be recursively merged.
 * If a property value is a string or number, it will directly overwrite the `target` property.
 *
 * @param target - The target object to merge properties into.
 * @param source - The source object containing properties to merge into the target object.
 * @returns A new object with merged properties from both `target` and `source`.
 */
export declare const deepMerge: (target: Record<string, unknown>, source?: Record<string, unknown>) => {
    [x: string]: unknown;
};