libevdev

For input, you should be able to compile things built against [libevdev](https://gitlab.freedesktop.org/libevdev/libevdev). It's a large API, but the core keyboard/mouse/js stuff should basically work. I could make a simplified header (for use in wasi-sdk) but also having this work directly will mean that anything built against this interface basically works, even if they are not using the lib.

The issue names libevdev and wasi-sdk but no repository files, tests, or entry points. Start by locating the existing input support and determining how libevdev-compatible APIs would fit the WASI target. Done means software built against the core libevdev keyboard, mouse, and joystick interfaces can compile and work.

Written by the indexing model from the issue text.