Basic filesystems support for Wasm target

[fzhinkin]

There's no FS support for Wasm, although it could be implemented on top of the WASI.

[fzhinkin]

First part, enabling filesystems for wasmJs: #256

[sureshg]

@fzhinkin just for the clarity when you say wasmJs, it's for running on node and not on browser and browser won't get file system support due to security sandboxing..rt?

[fzhinkin]

@sureshg, yes, that's correct. Browsers don't provide a proper fs API (well, there's a FileSystem API, but that's a whole different story), so when it comes to JS, kotlinx.io.files works only in NodeJs (or, theoretically, any other server-side JS engine compatible with Node).
However, there's a memfs library bringing an in-memory filesystem to browsers and providing node:fs-compatible API. It needs to be checked, but I guess it might allow using kotlinx-io fs-support in browsers.

[fzhinkin]

And the wasmWasi support: #257