Recording compatible runtimes

[oovm]

Motivation

I was working with jsr.io and realized that we might want to document which runtimes each package is compatible with.

For example, if I modify wasmtime and register some LLM-related functions, then such a runtime is a non-wasi standard runtime and needs to use a different interface check.

Such a runtime can be defined with a pure wit exported package, and users can specify such a dependency as the runtime in the meta information, and then other tools can check whether there are missing definitions.

Design

1. type: "runtime" is a special package type that does not depend on any package and only exports wit.

The meta information of the package can provide the github address of this runtime implementation, etc.

2. runtime-dependencies: {id: version} can record compatible runtime versions, and tools can download wit definitions for further type checking.