Add French support

[thomask-gh]

Hello, and first thank you for this plugin!
I would like it to have support for French, and I tried looking into the code of the parsers for other languages, but I’m not really sure how it works, nor how I can look into ZIM files to understand their structure and write a parser for them… How much effort do you think it would be to add support for the French language? :)

[abdnh]

You have to inspect the HTML structure to understand how to parse it. I'll add this to the todo list to look into (will probably take a few months)

[thomask-gh]

Ok, thanks, I will see if I can find the time to look into it before then!