Update wasm.md (#5880)

Mention lack of `webdev` integration

Fixes <Replace with issue link>

---

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.
- [x] This PR doesn't contain automatically generated corrections or
text (Grammarly, LLMs, and similar).
- [x] This PR follows the [Google Developer Documentation Style
Guidelines](https://developers.google.com/style) — for example, it
doesn't use _i.e._ or _e.g._, and it avoids _I_ and _we_ (first person).
- [x] This PR uses [semantic line
breaks](https://github.com/dart-lang/site-shared/blob/main/doc/writing-for-dart-and-flutter-websites.md#semantic-line-breaks)
of 80 characters or fewer.

<details>
  <summary>Contribution guidelines:</summary><br>

- See our [contributor
guide](https://github.com/dart-lang/site-www/blob/main/CONTRIBUTING.md)
for general expectations for PRs.
- Larger or significant changes should be discussed in an issue before
creating a PR.
- Code changes should generally follow the [Dart style
guide](https://dart.dev/effective-dart) and use `dart format`.
- Updates to [code
excerpts](https://github.com/dart-lang/site-shared/blob/main/doc/code-excerpts.md)
indicated by `<?code-excerpt` need to be updated in their source `.dart`
file as well.
</details>

Author: mit-mit

src/content/web/wasm.md

@@ -36,6 +36,11 @@ restrictions:
    [next-gen JS interop mechanism](/interop/js-interop/)
    is supported when compiling to Wasm.
 
+1. There is currently no support in the `webdev` tool for running
+   (`webdev serve`) or building (`webdev build`). The steps below
+   contain a temporary workaround. For details, see
+   [webdev issue 2206]({{site.repo.dart.org}}/webdev/issues/2296).
+
 ## Compiling your web app to Wasm {:#compiling-to-wasm}
 
 We've landed support in the `dart` CLI for invoking the