Better integration with the file system

[tidoust]

This includes:

• write access to the file system
• support for sparse files
• support for zero copy I/O operations
• multihreaded access instead of having to proxy through the main thread

Partially addressed by Origin Private File System.

Raised in:

• Bringing Desktop-Class Creative Expression to the Web
• A Non-linear Video Editor built with WebAssembly

[mkruisselbrink]

https://github.com/WICG/file-system-access/blob/main/AccessHandle.md (which currently is largely another API to access files in the same Origin Private File System) tries to better address things like zero copy I/O operations as well.