Document no_std usage

README.md

@@ -23,9 +23,18 @@ If this overhead is problematic, you can disable it by instead specifying the fo
 
 ```toml
 [dependencies]
-blurhash = { version = "0.2.3", default-features = false }
+blurhash = { version = "0.2.3", default-features = false, features = ["std"] }
 ```
 
+Blurhash can also run in `no_std` environments by disabling the default features:
+
+```toml
+[dependencies]
+blurhash = { version = "0.2.3", default-features = false, features = ["fast-linear-to-srgb"] }
+```
+
+Blurhash requires Rust 1.82 or later when using `no_std`.
+
 ### Encoding
 ```rust
 use blurhash::encode;

src/lib.rs

@@ -1,5 +1,4 @@
 #![cfg_attr(not(any(test, feature = "std")), no_std)]
-#![cfg_attr(not(any(test, feature = "std")), feature(error_in_core))]
 
 //! A pure Rust implementation of [woltapp/blurhash][1].
 //!