Update Mathlib Note in README.md

README.md

@@ -5,9 +5,12 @@ The project started and still emerges mostly through student projects. You are w
 
 ## Notes on Setup:
 
-Using `elan` / `lake`:  
+Using [`elan`](https://github.com/leanprover/elan) / `lake`:  
 ```
 lake build
 ```
-This will download mathlib4 and build the project. Currently it might still break, because
-mathlib4 has no releases yet. (Todo: update this when mathlib4 has a release)
+This will download mathlib4 and build the project.  
+To prevent building mathlib yourself, you can run the following to fetch precompiled files.
+```
+lake exe cache get
+```