no-std::no-alloc not displayed

The no-alloc variant of the no-std category has been introduced on crates.io in January by yours truly.

When a crate uses this, libs.rs doesn't show the no-std box it usually shows above the title of no-std crates.

Examples: https://lib.rs/crates/coap-handler-implementations is no-std::no-alloc; https://lib.rs/crates/coap-message hasn't been updated since the introduction of that category and is still no-std only.

Please consider either showing no-std on such crates, or giving them a new tag (no-alloc implies no-std, so it could be just that).