Publish web_embedding (#1777)

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[CLA]: https://cla.developers.google.com/
[Discord]: https://github.com/flutter/flutter/wiki/Chat
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md


Co-authored-by: Mark Thompson
<2554588+MarkTechson@users.noreply.github.com>
Co-authored-by: David Iglesias <ditman@gmail.com>

Co-authored-by: Mark Thompson <2554588+MarkTechson@users.noreply.github.com>
Co-authored-by: David Iglesias <ditman@gmail.com>

web_embedding/README.md

@@ -0,0 +1,11 @@
+# web_embedding
+
+This directory contains examples of how to embed Flutter in web apps (without iframes):
+
+* **element_embedding_demo**: Modifies the index.html of a flutter app so it is
+  launched in a custom `hostElement`. This is the most basic embedding example.
+* **ng-flutter**: A simple Angular app (and component) that replicates the above
+  example, but in an Angular style.
+
+Check the `README.md` of each example for more details on how to run it, and the
+"Points of Interest" it may contain.