Add a note for contributors installing fourmolu

CONTRIBUTING.md

@@ -190,15 +190,24 @@ of their patch is not influenced by their setup or implicit knowledge of the sys
 
 ## Code Style
 
-We use automated formatting with Fourmolu to enforce a unified style across the code bases. It is checked in the CI process.
-After installing Fourmolu 0.12, there are some makefile targets to help formatting
-the code base.
-
+We use automated formatting, checked in the CI process, to enforce a unified
+style across the code bases and have these makefile targets to help formatting
+the code base:
 
 * `make style` - Format the `Cabal`, `Cabal-syntax` and `cabal-install` directories.
 * `make style-modified` - Format files modified in the current tree.
 * `make style-commit COMMIT=<ref>` - Format files modified between HEAD and the given reference.
 
+> [!NOTE]
+> We use `fourmolu-0.12.0.0` for formatting. If installing it with `cabal
+> install`, please make sure to use a version of GHC >= 9.2.1 && < 9.8. That it
+> requires `GHC2021` sets the lower bound and its reliance on `ghc-lib-parser`
+> sets the upper bound on GHC versions. The command for installing it this way is:
+>
+> ```
+> $ cabal install fourmolu-0.12.0.0 --overwrite-policy=always --ignore-project
+> ```
+
 ## Whitespace Conventions
 
 We use automated whitespace convention checking. Violations can be fixed by