Add an llm.txt like Angular 20

[stanlrt]

llm.txt files are becoming popular to enhance LLM's performance when generating code for a framework/lib. Angular 20 just added one (angular/angular#61285). However, I find it quite basic and it forces LLMs to index linked web pages. Ark UI's is more comprehensive: https://ark-ui.com/llms-solid.txt

It'd be cool for Solid to do the same, especially since its similarity with React can confuse LLMs (although it is one of Solid's main advantages to gain market share).