Allow wkg to trust system root CA

[rajsite]

When I run wkg on my IT-managed Windows machine I get the following error:

 > wkg wit fetch
 
2026-03-23T19:39:14.001995Z  WARN wasm_pkg_client::metadata: Error fetching registry metadata error=RegistryMetadataError(error fetching registry metadata from "https://wasi.dev/.well-known/wasm-pkg/registry.json"

Caused by:
    0: error sending request for url (https://wasi.dev/.well-known/wasm-pkg/registry.json)
    1: client error (Connect)
    2: invalid peer certificate: UnknownIssuer)

My hunch is that the IT configuration requires using the system root CA for HTTP requests, see similar:

• spin issue and PR.
• servo issue and PR

There is a related issue asking for extra root certs / accepting invalid certs: #127

I think this issue to trust the system root CA (and while independent the related issue for extra roots / accepting invalid certs) could be handled following the pattern from the spin and servo PRs by leaning on rustls-platform-verifier.