wasm: Add example with two modules

[codefromthecrypt]

We need another example where one module exports a function another module imports (both compiled by TinyGo with -target=wasm). Making the example here has the advantage of being testable. That said, the current site content doesn't make it easy to discover which examples exist. There may be some work on that side to improve discovery.

Note that a PR to affect the site is not in this repo (https://github.com/tinygo-org/tinygo-site/blob/release/content/docs/guides/webassembly.md)

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We have recently a bit more discovery in wasm examples recently. Notably, you can see a list of sorts of examples. However, it isn't on the release branch, yet, so not navigable from the website guide.

minor note that a guide should include a end to end example of a module exporting a function, another module importing it, and then executing the resulting modules. something along this line.

Originally posted by @james-lawrence in #3147 (comment)