Support to WebAssembly build

[ribeiromiranda]

What this PR does / why we need it:
To build and execute the webassembly in a browser, electron, etc

GOOS=js GOARCH=wasm $(GO)  build -o out.wasm ./source/

Special notes for reviewers:
In my tests, the only need to change was the file manipulation.

[spolti]

Maybe we can have a issue describing better why it is needed and maybe a few instructions about how to use it?

[ricardozanini]

@spolti as I understood, this is needed for WebAssembly use cases.

[spolti]

@spolti as I understood, this is needed for WebAssembly use cases.

Yes, but it would be nice to have a documented use case.

[ricardozanini]

Not sure what you mean by documented use case, but I'm honestly curious to know more about @ribeiromiranda 's use case for the SDK and WebAssembly :)

[ribeiromiranda]

I'm developing a platform called fermions for developers to design, build, test CloudEvents and Serverless workflow. To build a cross-platform desktop app, I'm using electron.

The fermions-workflow (multiple platforms) use this sdk-go, builded with WebAssembly it's possible run the workflows in electron or other web browser.