Add clippy relnotes (#545)

Author: Manishearth

posts/2020-03-12-Rust-1.42.md

@@ -169,8 +169,9 @@ In this release, if you are using Cargo, [you no longer need this line when work
 ### Other changes
 
 [relnotes-cargo]: https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-142-2020-03-12
+[relnotes-clippy]: https://github.com/rust-lang/rust-clippy/blob/master/CHANGELOG.md#rust-142
 
-There are other changes in the Rust 1.42.0 release: check out what changed in [Rust][notes] and [Cargo][relnotes-cargo].
+There are other changes in the Rust 1.42.0 release: check out what changed in [Rust][notes], [Cargo][relnotes-cargo], and [Clippy][relnotes-clippy].
 
 
 ### Compatibility Notes