feat: Switch to platform-specific TLS/SSL certificate verification

Use rustls-platform-verifier to verify certificates with the
OS/platform's standard methods, including the system's standard CA trust
store.  See rustls-platform-verifier's documentation for details on each
platform.¹

Previously, the system's trust store was ignored in favor of a baked in
and unconfigurable trust store provided by webpki-roots.

Updates reqwest as necessary to ensure a single compatible rustls
version remains in use.  Updates wasm-bindgen as necessary for the newer
reqwest.

¹ <https://github.com/rustls/rustls-platform-verifier/blob/v/0.3.4/README.md>

Resolves: <#726>
Related-to: <#1527>