Enable rkyv's size_32 feature for dev-dependencies

So that when building `--all-features` (turns on `rkyv`) `--all-targets`
(builds `benches` etc), there is no error that at least one `size_xx`
must be set.

Cargo.toml

@@ -48,13 +48,14 @@ mint = { version = "0.5.8", optional = true, default-features = false }
 rand = { version = "0.8", optional = true, default-features = false }
 serde = { version = "1.0", optional = true, default-features = false }
 rkyv = { version = "0.7", optional = true, default-features = false }
-bytecheck = { version = "0.6", optional = true, default-features = false}
+bytecheck = { version = "0.6", optional = true, default-features = false }
 libm = { version = "0.2", optional = true, default-features = false}
 
 [dev-dependencies]
 # rand_xoshiro is required for tests if rand is enabled
 rand_xoshiro = "0.6"
-rkyv = "0.7"
+# Set a size_xx feature so that this crate compiles properly with --all-targets --all-features
+rkyv = { version = "0.7", features = ["size_32"] }
 serde_json = "1.0"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]