feat(docs): add Chinese translation (jump link)

[100ask]

I created this PR with a new branch, the old PR: #5750

[kisvegabor]

Looks good! Thank you! 😊

[PGNetHun]

1. Some minor changes needed
2. Sorry, but I think we should show the external link ( https://lvgl.100ask.net/ ) on the home page, or in header/footer instead of adding same link_to_translation to every doc file. New doc files will not contain it (ppl might forget to add), and btw there could be other translations too, not only chinese, so having a link in header/footer/sidenav to external sites with the translations is better.

[100ask]

2. instead of adding same link_to_translation to every doc file. New doc files will not contain it (ppl might forget to add),

Good suggestion! I will improve it today.

[100ask]

2. and btw there could be other translations too

What do you think? @kisvegabor

[PGNetHun]

Good changes, thanks, only some minor comments are added.

PS:
you don't have to squash commits in your branch, simply add a new commit, so reviewers can see what is changed since last review (since last commit).
Then after PR is approved, we do a squash merge, and in the end only 1 commit will go to master branch. But till then it is good to see all commits and change commits in feature branch.

[kisvegabor]

Sorry, but I think we should show the external link ( https://lvgl.100ask.net/ ) on the home page, or in header/footer instead of adding same link_to_translation to every doc file.

What about near to the link?

[100ask]

Sorry, but I think we should show the external link ( https://lvgl.100ask.net/ ) on the home page, or in header/footer instead of adding same link_to_translation to every doc file.

What about near to the link?

1. Not obvious, may not notice.
2. When reading on a small screen, it becomes difficult, even invisible:
   

I think it's appropriate to put it at the beginning of the text:

[PGNetHun]

Yes, I think at the moment it is enough to add to top of page (like in ESP-IDF), so later we might implement other option.

(I personally prefer having a language selector dropdown / button on top of sidenav, or top-right of page, that we don't need to search, and does not reserve/waste too much space on screen)

[kisvegabor]

It's unlikely that we will add more translations in the future due to maintenance issues. China is special because:

• We have a lot of users in China
• Many people don't know English
• Websites outside of China are super slow