Add guidance for structuring local file dependencies

[brooksmtownsend]

I wanted to set up some local interface dependencies for wkg to fetch, and I could find the right way to structure the filesystem. With some trial/error and setting up the code, I did eventually find the right structure (this is the folder that I pointed to for wasi.dev):

drwxr-xr-x     - brooks 29 Oct 10:40  ./
drwxr-xr-x     - brooks 29 Oct 10:42  └── wasi/
drwxr-xr-x     - brooks 29 Oct 10:45     ├── http/
.rw-r--r--   38k brooks 29 Oct 10:45     │  ├── 0.2.0.wasm
drwxr-xr-x     - brooks 29 Oct 10:44     ├── keyvalue/
.rw-r--r--   13k brooks 29 Oct 10:43     │  ├── 0.2.0-draft.wasm
drwxr-xr-x     - brooks 29 Oct 10:45     ├── logging/
.rw-r--r--  1.4k brooks 29 Oct 10:45     │  ├── 0.1.0-draft.wasm

I think some guidance on the fact that files should be stored in the form of <namespace-folder>/<package-folder>/<version>.wasm would be great, or if I'm missing this please just let me know what I misinterpreted! Happy to contribute this to the README as well if that's desired, or an external docs site.

[thomastaylor312]

Yep that looks correct. Feel free to add to the README