Add an option to automatically run wasm-opt on wasm binaries

It is possible to optimize WASM binaries after they have been built using something like [wasm-opt](https://github.com/WebAssembly/binaryen). There are various modes and different kind of optimizations that can be done (size, speed and some things not enabled by default etc.). We should investigate if this is viable to add in some way in order to improve performance. I am worried that this might take a long time to run.

Start by examining how this repository builds and handles WASM binaries, then evaluate integrating wasm-opt and its size, speed, and non-default optimization modes. Determine whether the runtime cost is acceptable and what configuration would be needed; the work is done when a viable, documented approach is established or the integration is shown not to be suitable.

Written by the indexing model from the issue text.