docs(guide): Talk about removing unused features

Author: epage

src/doc/src/guide/build-performance.md

@@ -127,3 +127,21 @@ it can be easy to miss that a dependency is no longer used and can be removed.
 Trade-offs:
 - ✅ Faster full build and link times
 - ❌ May incorrectly flag dependencies as unused or miss some
+
+### Removing unused features from dependencies
+
+Recommendation: Periodically review unused features from dependencies for removal using third-party tools like
+[cargo-features-manager](https://crates.io/crates/cargo-features-manager),
+[cargo-unused-features](https://crates.io/crates/cargo-unused-features).
+
+When changing code,
+it can be easy to miss that a dependency's feature is no longer used and can be removed.
+This can reduced the number of transitive dependencies being built or
+reduce the amount of code within a crate being built.
+When removing features, extra caution is needed because features
+may also be used for desired behavior or performance changes
+which may not always be obvious from compiling or testing.
+
+Trade-offs:
+- ✅ Faster full build and link times
+- ❌ May incorrectly flag features as unused