Beginner Repository Build Documentation

[mprater]

Add beginner/introductory focused instructions for installing any necessary libraries and building the contents of the OSL repo. This would document all the steps necessary to successfully build all the OSL repo contents.

I have a Siggraph 2025 OSL Lab submission that could be re-designed to cover this exact material, which could then be added to the repository. The lab materials could also cover the use of osltoy and/or testrender as tools for .osl shader testing and/or development.

[mprater]

The latest install.md installation instructions are a good start: https://github.com/AcademySoftwareFoundation/OpenShadingLanguage/blob/main/INSTALL.md

[mprater]

I've begin detailing the process of taking a fresh Rocky 9 system from zero to fully compiling/functional OSL repo content.