Nebula pages updated

As our Nebula user base is expanding, more and more people look for more information about what Nebula is and what it can do. As a result, we have updated and greatly expanded the scope of the Nebula page on the Network Institute website. The pages are now more welcoming to both inexperienced and seasoned LLM users. Inexperienced users can find out more about what LLMs are, their creation, pros, cons and simple use cases. Experienced users can discover some advanced use cases of Nebula, our infrastructure setup and other more esoteric topics regarding our platform.