Notepad would absolutely work, but I’d recommend downloading the free Notepad++ and getting one of the markdown viewer plugins.
i don’t actually know how small. It might be chapters at first, which is just Heading 1 (one # in front) I believe. Essentially, comfortable to read and search. Web pages aren’t supposed to be 500 pages long like it is now.
if you don’t know how to do GitHub, that’s ok. I can manage that part of I just get files.