Update translation docs

[agjohnson]

We do a bad job of explaining how to contribute documentation for readthedocs docs and UI.

[mukul09]

I want to work on this issue, as far as I got your point is that the contribute documentation should be in other languages also. right?

[stsewd]

@mukul09 this issue is about improving the steps for contributing to translations (but also looks like about contributing to documentation and design).

Here are a links about the current docs:

• https://docs.readthedocs.io/en/latest/i18n.html?highlight=translations#administrative-tasks
• https://docs.readthedocs.io/en/latest/contribute.html#helping-on-translations (here there is just a link!)

Note: I think the steps about contributing to documentation are covered on #3498.

[agjohnson]

@humitos added a guide on managing translations. That was the piece i was looking to start with here. Closing this issue.