Improve readme description of features

README.md

@@ -61,6 +61,20 @@ If you want to use bit-vec in a program that has `#![no_std]`, just drop default
 bit-vec = { version = "0.6", default-features = false }
 ```
 
+If you want to use serde with the alloc crate instead of std, just use the `serde_no_std` feature:
+
+```toml
+[dependencies]
+bit-vec = { version = "0.6", default-features = false, features = ["serde", "serde_no_std"] }
+```
+
+If you want [borsh-rs](https://github.com/near/borsh-rs) support, include it like this:
+
+```toml
+[dependencies]
+bit-vec = { version = "0.6", features = ["borsh"] }
+```
+
 <!-- cargo-rdme start -->
 
 ### Description