Add a note about lookbehind in RegExp

Author: octet-stream

src/util/normalizeValue.ts

@@ -8,6 +8,7 @@
  * @api private
  */
 export const normalizeValue = (value: unknown): string => String(value)
+  // TODO: Revert this to /\r(?!\n)|(?<!\r)\n/g when all browsers will support lookbehind in RegExp. See: https://github.com/octet-stream/form-data-encoder/issues/5
   .replace(/\r|\n/g, (match: string, i: number, str: string) => {
     if (
       (match === "\r" && str[i + 1] !== "\n")