docs: specify ffmpeg version and add note on libclang-*

README.md

@@ -4,14 +4,15 @@
 ## How to build?
 ### Linux
 1. Install rust
-1. Install ffmpeg, sdl2, sdl2_mixer, sdl2_image, sdl2_ttf.
+1. Install ffmpeg 7.*, sdl2, sdl2_mixer, sdl2_image, sdl2_ttf.
     - For instructions on sdl2 installation, see [rust-sdl2 README](https://github.com/Rust-SDL2/rust-sdl2).
+    - You may have to install libclang on some platforms (e.g. Raspberry Pi)
 1. Run `cargo build`
 1. When running the game, `assets` directory and `music` directory should be in the working directory.
 
 ### Mac OS
 1. Install rust
-1. Install ffmpeg, sdl2, sdl2_mixer, sdl2_image, sdl2_ttf.
+1. Install ffmpeg 7.*, sdl2, sdl2_mixer, sdl2_image, sdl2_ttf.
     - For instructions on sdl2 installation, see [rust-sdl2 README](https://github.com/Rust-SDL2/rust-sdl2).
 1. Type `export LIBRARY_PATH="$LIBRARY_PATH:$(brew --prefix)/lib"` to your terminal.
 1. Run `cargo build`