Use github for documentation. For multiple services, use separate repo. Tie your tech doc to product
Create readme.md in your repo and add there:
Documentation can be of different type, depending on its purpose and end-user (specification document, maintenance sheet, integration document shared with other vendors etc.).This recommendation discusses documentation systems that is needed for web-app as a product for internal engineers.It does not refer to public API documentation, public knowledge center or how-to articles.
These are all optional, pick ones that are relevant to you. "Priority" column here is just to allow sorting of priorities
In progress, structure is not clear yet
Multiple services are usually grouped by their role for the product. Project is a big feature group of web-app or a separate product / stand-alone portal
Diagrams are visually pleasing, but maintaining them is harder. They are also not as searchable, so keep them to minimum