Add note in README/Tutorial regarding CPP support (#1224)

* add note regarding CPP support

* clarified support for Literal Haskell

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: tittoassini

plugins/hls-eval-plugin/README.md

@@ -72,7 +72,7 @@ double a = a + a
 -- 22
 ```
 
-Both plain Haskell and Literate Haskell (Bird-style only) source files are supported.
+Modules that use CPP and Literate Haskell (Bird-style only) modules are also supported (for GHC >= 8.8).
 
 # Test Components