feat: 🎸 harden WritableStream usage

Author: streamich

src/fsa/CoreFileSystemWritableFileStream.ts

@@ -5,10 +5,13 @@ import { ERROR_CODE } from '../core/constants';
 import { newNotAllowedError } from './util';
 import { FLAGS, MODE } from '../node/constants';
 
+declare const require: any;
+const WS = (typeof WritableStream === 'undefined' ? require('stream/web').WritableStream : WritableStream) as typeof WritableStream;
+
 /**
  * @see https://developer.mozilla.org/en-US/docs/Web/API/FileSystemWritableFileStream
  */
-export class CoreFileSystemWritableFileStream extends WritableStream implements IFileSystemWritableFileStream {
+export class CoreFileSystemWritableFileStream extends WS implements IFileSystemWritableFileStream {
   private _fd: number | undefined;
   private _position: number = 0;
   private _closed = false;

src/node-to-fsa/NodeFileSystemWritableFileStream.ts

@@ -51,14 +51,17 @@ interface SwapFile {
   ready?: Promise<void>;
 }
 
+declare const require: any;
+const WS = (typeof WritableStream === 'undefined' ? require('stream/web').WritableStream : WritableStream) as typeof WritableStream;
+
 /**
  * Is a WritableStream object with additional convenience methods, which
  * operates on a single file on disk. The interface is accessed through the
  * `FileSystemFileHandle.createWritable()` method.
  *
  * @see https://developer.mozilla.org/en-US/docs/Web/API/FileSystemWritableFileStream
  */
-export class NodeFileSystemWritableFileStream extends WritableStream implements IFileSystemWritableFileStream {
+export class NodeFileSystemWritableFileStream extends WS implements IFileSystemWritableFileStream {
   protected readonly swap: SwapFile;
 
   constructor(