TinyGo allocation example

This example shows how to pass strings in and out of a Wasm function defined in TinyGo, built with tinygo build -o greet.wasm -scheduler=none -target=wasi greet.go

$ go run greet.go wazero
wasm >> Hello, wazero!
go >> Hello, wazero!

Under the covers, greet.go does a few things of interest:

• Uses unsafe.Pointer to change a Go pointer to a numeric type.
• Uses reflect.StringHeader to build back a string from a pointer, len pair.
• Relies on CGO to allocate memory used to pass data from TinyGo to host.

See https://wazero.io/languages/tinygo/ for more tips.