Declare browser 'stream' fallback in package.json imports

The browser field does not seem to be properly processed by Rollup.

Unclear if the 'default' condition is ever relevant, but the same fallback
as browser is used, since it's only needed to throw a more user-friendly error.

lib/browser-fallbacks.js

@@ -0,0 +1 @@
+export const NodeReadableStream = null;

lib/util.js

@@ -1,6 +1,8 @@
 /* eslint-disable no-prototype-builtins */
 import { isArrayStream } from './writer.js';
-import { Readable as NodeNativeReadableStream } from 'stream';
+
+// eslint-disable-next-line import/no-unresolved
+import { Readable as NodeNativeReadableStream } from '#node:stream'; // conditional entrypoint, see package.json
 const isNode = typeof globalThis.process === 'object' &&
   typeof globalThis.process.versions === 'object';
 

package.json

@@ -11,10 +11,17 @@
     "types": "./lib/index.d.ts",
     "import": "./lib/index.js"
   },
+  "imports": {
+    "#node:stream": {
+      "node": "stream",
+      "browser": "./lib/browser-fallbacks.js",
+      "default": "./lib/browser-fallbacks.js"
+    }
+  },
   "types": "./lib/index.d.ts",
   "main": "./lib/index.js",
   "browser": {
-    "stream": false
+    "#node:stream": false
   },
   "engines": {
     "node": ">= 16.5.0"
@@ -31,7 +38,7 @@
   "homepage": "https://github.com/openpgpjs/web-stream-tools#readme",
   "devDependencies": {
     "@openpgp/jsdoc": "^3.6.11",
-    "@types/node": "^18.11.9",
+    "@types/node": "^20.11.4",
     "@typescript-eslint/eslint-plugin": "^5.59.6",
     "@typescript-eslint/parser": "^5.59.6",
     "chai": "^4.3.7",