/**
 * https://github.com/sveltejs/kit/blob/e3544597bee62a43a0254490532f1f3663703d2d/packages/kit/src/exports/vite/utils.js#L72
 *
 * Merges b into a, recursively, mutating a.
 * @param {Record<string, any>} a
 * @param {Record<string, any>} b
 */
export function mergeInto(a: Record<string, any>, b: Record<string, any>): Record<string, any>;