[js/web] add "browser" field to support parcel v2 (microsoft#20422)

### Description

As described in latest discussion in microsoft#19915, parcel v2 without using the
[new resolver](https://parceljs.org/blog/v2-9-0/#new-resolver) will not
work correctly with onnxruntime-web. There are still users who uses
parcel with default resolver, so add this deprecated field "browser"
back for backward compatibility. This PR also corrects the "main" field,
which is for old resolver for Node.js.

js/web/package.json

@@ -64,7 +64,8 @@
     "numpy-parser": "^1.2.3",
     "strip-json-comments": "^5.0.0"
   },
-  "main": "dist/ort-web.node.js",
+  "main": "dist/ort.node.min.js",
+  "browser": "dist/ort.min.js",
   "exports": {
     ".": {
       "node": "./dist/ort.node.min.js",