Rewrite

[WyriHaximus]

This is a full rewrite of this package including the following features/changes:

• ext-uv adapter
• child process adapter
• fallback (blocking) adapter (for native Windows)
• simplified the internals to remove unnecessary complexity
• file_get_contents/file_put_contents like API to read/write from/to files
• start has become an object instead of an array

This PR doesn't include the following features/changes as those will be added in with followup PR's:

• ext-eio adapter
• macos support
• mode support to define permissions when creating files/directories
• symlinks read/creating/deleting
• deleting of directories

cc: @SimonFrings

[WyriHaximus]

@clue @SimonFrings This PR is now fully ready for review. The green build can be found here. And a readable render of the readme here.

[WyriHaximus]

@SimonFrings Thanks! Just updated this PR with your suggestions :+1:

[WyriHaximus]

@clue :ship: :it: !

I agree with everything that's been said, so I only briefly eyeballed this. This may not be perfect (yet), but it's definitely a major improvement over the current experimental filesystem implementation. Let's get this in as-is and build on top of this with future PRs +1

Already on it! https://github.com/reactphp/filesystem/pull/99