Add llms-full.txt file to help LLM systems better understand and utilize docs

[aglitchman]

"AI" tools for programmers like Cursor can index the documentation of a particular project and this helps a lot to improve the context of the LLM.

These tools can also index entire sites, but as it usually happens, the result is not very good, because the result includes a lot of unnecessary information. This also applies to the Defold documentation site.

Since the end of 2024, the idea of creating one large file with all the project documentation in a simple format (Markdown) that can be given as context to the LLM has gained popularity.

Request: add the llms-full.txt file to the Defold documentation site.

Detailed explanation: https://medium.com/towards-data-science/llms-txt-414d5121bcb3

[aglitchman]

Documentation on how to write the file: https://llmstxt.org/
Catalog of examples: https://llmstxt.site/

[britzl]

We can either add a GitHub Action to this repository that on every commit runs a script to build the llms-full.txt OR we move this logic to the existing doc processing done here https://github.com/defold/defold.github.io/blob/master/update.py#L315