feat(rust): add webassembly example

[eduardomourar]

aws-doc-sdk-examples Pull Request

I'm submitting a new SDK code example

The example depends on this PR.

Confirm you have met the following minimum requirements:

• Add the following copyright notice to the top of each file. See the LICENSE agreement for the terms of the copyright.

Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
SPDX-License-Identifier: Apache-2.0

• Create unit tests for all paths through the code, and confirm that the all the tests pass. For recommendations, see How we test code examples.
• Run a linter against all code and implement the resulting suggestions. For recommendations, see Linters run on check in.
• Add minimum usage documentation as comments in the code. For recommendations, see Code comment guidelines.

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[DavidSouther]

Hey, @eduardomourar, just wanted to let you know I am working on a review for this PR, but I need to do a bit of research on the WebAssembly side of things first! Thank you for your contributions!

[DavidSouther]

Thank you again for this! It's a feature that's been in my backlog for an April timeframe, but this definitely jumpstarts that :) Most of the review comments are small nits in the HTML/JS side; the Rust looks really solid. As I mention in a specific comment, this needs a larger User Guide entry, but this is a great start.

[DavidSouther]

I'm adding @lkdavies, our team's editor, for review of the README and prose.

[lkdavies]

Editorial comments