Update posts/2025-01-09-Rust-1.84.0.md

Co-authored-by: Weihang Lo <weihanglo@users.noreply.github.com>

Author: Mark-Simulacrum

posts/2025-01-09-Rust-1.84.0.md

@@ -39,7 +39,8 @@ versions.
 
 The new resolver will be enabled by default with the 2024 edition (expected to
 stabilize in 1.85), but can be enabled as of 1.84 by setting
-`resolver.incompatible-rust-versions = "fallback"`.
+[`package.resolver = "3"`](https://doc.rust-lang.org/cargo/reference/resolver.html#resolver-versions) in the Cargo.toml manifest file, or
+[`resolver.incompatible-rust-versions = "fallback"`](https://doc.rust-lang.org/cargo/reference/config.html#resolverincompatible-rust-versions) in the Cargo configuration file.
 
 TODO: Should we talk about resolver v3 and/or recommend that as the path to enabling instead?