Aside from LaTeX markup, there are only 2 macros you may be aware of.
"\RU{russian text}" and "\EN{english text}" used in places where the string of one specific language should be present.
Read here.
Commenting right in the LaTeX source code may be good idea. LaTeX comments are started with percent ('%') sign.
It's fine to write comments like: "I would love to read more about this and that right here at this place" and/or "It's also a great idea to mention this and that right here".
When time will allow me, I will try to extend these parts.
Feel free to create pull requests for this.
Otherwise, just send me email: dennis(a)yurichev.com.
Do not worry to contribute more errors and mistakes - I'll fix them during merging.
Do not worry to bother me while writing me about any petty mistakes you found, even if you are not very confident. I'm writing for beginners, after all, so beginners' opinions and comments are crucial for my job.