docs: add a link to the official lua 5.2.1

Docs/LinuxOsxInstall.md

@@ -24,7 +24,8 @@ Note that [the version available on Flathub](https://flathub.org/apps/details/co
 ## OSX installation instructions
 Below are the instructions for the arm64 Macs. To use them for Intel Macs, please apply the changes to the folder `Yafc/lib/osx` instead of `Yafc/lib/osx-arm64`.
 - [Install dotnet core (v8.0 or later)](https://dotnet.microsoft.com/download)
-- Download the lua5.2.1 source, copy the [.patch](https://github.com/shpaass/yafc-ce/blob/master/lua-5.2.1.patch) file and apply.
+- Download and extract the [lua 5.2.1 source code](https://www.lua.org/ftp/lua-5.2.1.tar.gz)
+- Apply the [.patch](https://github.com/shpaass/yafc-ce/blob/master/lua-5.2.1.patch) file to the extracted lua source code.
 - Modify the `src/Makefile` to include the following two lines. Note that the second line must start with a tab:
 ```
 liblua.dylib: $(CORE_O) $(LIB_O)
@@ -52,4 +53,4 @@ libSDL2_tff.dylib
 - Run `build.sh` to build Yafc. If you get an error `grep: invalid option -- P`, then you need to either remove the mentions of `VERSION` from `build.sh` so `grep` is not used, or you need to install GNU grep with `brew install grep` and change `grep` in `build.sh` to `ggrep`.
 - The folder `Build/OSX-arm64` will contain all of the arm64 files and should run in place. It will also create an archive `OSX-arm64.tar.gz` for the distro.
 - Make sure you have OpenGL available.
-- To run the app, either use `dotnet Yafc.dll` in the terminal, or run `Yafc` as an executable.
+- To run the app, either use `dotnet Yafc.dll` in the terminal, or run `Yafc` as an executable.