installation instructions might need an update

I followed the compiling instructions for fedora, but when I run "cmake .." i get this error:
```
-- The CXX compiler identification is unknown
CMake Error at CMakeLists.txt:9 (project):
  No CMAKE_CXX_COMPILER could be found.
```

This is resolved when I install
`sudo dnf install gcc-c++`
(as suggested by chatgpt)