Where to start learning about the development of plugins and extensions for the Firefox Quantum browser (for those who don't really know English)?

Question

Mozilla Firefox

Hello! In general, the title of the question already contains enough information about what kind of answer to the question you would like to receive.
It is clear that there is such a link https://developer.mozilla.org/en-US/docs/Mozilla/A... to documentation on this issue, but it is in English.
Also, using search engines on the issue, it is possible to find some articles on Habré, while for some of them it is not clear how suitable they are for the version of the Quantum browser, since many plugins and extensions stopped working with the release of this version.
A huge plus in the answer will be the presence of a link to an example of an extension (its source code), so that you can unzip and see what is there and try to install it.

Answer 1

I would suggest starting with pulling up English. No kidding. You don't currently have a translation for the Browser API Documentation. Then there will be no translation in another subject. And where a translation is found, it is usually not up to date or contains controversial decisions, unsuccessful terms and other errors.
And you can pull up English just by studying the documentation. This is easier than fiction, as many of the terms will already be familiar or have the same roots.

Answer 2

From learning English enough to read the documentation.

Answer 3

On mozdev like everything is clearly described. Didn't experience any difficulty reading their almost step by step guide. What can be incomprehensible in articles that are more than half composed of code?
Any fox extension can be unpacked. This is a simple zip archive.