[docs] Update LLVM version

Author: aaronj0

README.md

@@ -77,19 +77,20 @@ git clone --depth=1 https://github.com/compiler-research/cppyy-backend.git
 ```
 
 #### Setup Clang-REPL 
-Clone the 17.x release of the LLVM project repository.
+Clone the 18.x release of the LLVM project repository.
 ```
-git clone --depth=1 --branch release/17.x https://github.com/llvm/llvm-project.git
+git clone --depth=1 --branch release/18.x https://github.com/llvm/llvm-project.git
 cd llvm-project
 ```
-Get the following patches required for development work. To apply these patches on Linux and MacOS execute the following command
+
+For Clang 16 & 17, the following patches required for development work. To apply these patches on Linux and MacOS execute the following command(substitute `{version}` with your clang version):
 ```
-git apply -v ../CppInterOp/patches/llvm/clang17-*.patch
+git apply -v ../CppInterOp/patches/llvm/clang{version}-*.patch
 ```
 and
 ```
 cp -r ..\CppInterOp\patches\llvm\clang17* .
-git apply -v clang17-1-NewOperator.patch
+git apply -v clang{version}-*.patch
 ```
 on Windows.