Fix CHANGELOG.md links to pull-requests

CHANGELOG.md

@@ -1,8 +1,12 @@
 # Unreleased
 
-- Rename `StableHasherResult` to `FromStableHash` (#8)
-- Use new-type for returned-hash of `SipHasher128`(`Hash`) (#8)
-- Introduce multi hasher support (#8)
-- `StableHasher::finish` now returns a small hash instead of being fatal (#6)
-- Remove `StableHasher::finalize` (#4)
+- Rename `StableHasherResult` to `FromStableHash` [#8][pr8]
+- Use new-type for returned-hash of `SipHasher128`(`Hash`) [#8][pr8]
+- Introduce multi hasher support [#8][pr8]
+- `StableHasher::finish` now returns a small hash instead of being fatal [#6][pr6]
+- Remove `StableHasher::finalize` [#4][pr4]
 - Import stable hasher implementation from rustc ([db8aca48129](https://github.com/rust-lang/rust/blob/db8aca48129d86b2623e3ac8cbcf2902d4d313ad/compiler/rustc_data_structures/src/))
+
+[pr8]: https://github.com/rust-lang/rustc-stable-hash/pull/8
+[pr6]: https://github.com/rust-lang/rustc-stable-hash/pull/6
+[pr4]: https://github.com/rust-lang/rustc-stable-hash/pull/4