Support no-std (#506)

- **Support `no-std`**
- **Update categories**

Cargo.toml

@@ -5,6 +5,7 @@ edition = "2024"
 description = "impl GlobalAlloc for bdwgc"
 repository = "https://github.com/raviqqe/bdwgc-alloc"
 license = "MIT"
+categories = ["api-bindings", "memory-management", "no-std", "no-std::no-alloc"]
 
 [dependencies]
 libc = "0.2.178"

src/lib.rs

@@ -1,6 +1,5 @@
 #![doc = include_str!("../README.md")]
-
-extern crate alloc;
+#![no_std]
 
 mod error;