docs: 2 new pages: "Sync & Collaboration Tools" and "Translation.io"

[MichaelHoste]

I finally made some documentation for the "Sync & Collaboration Tools" (see #1107).

There is a small introduction that explains how to translate an app in a regular workflow (.po files and text editor or PoEdit), and that also explains how to scale that up with a sync & collaboration tool if the application becomes too big (source text that doesn't stop evolving and lots of target languages). The diagrams are mine so there are no copyright issues.

I also explained the process to integrate new tools into Lingui if other services want to add theirs in the future.

There is a second page that describes Translation.io (features, installation, usage). This page contains many animated gifs that are hosted directly on Translation.io. I didn't want to push them on this repository because they are quite big. I hope it's ok with you.

This PR is obviously not completely selfless and we hope that there will be some positive synergies between Lingui and Translation.io, but we tried to create a structure so that other competing services could easily be added in the future, providing more value for Lingui users.

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Many small Sphinx warnings were also fixed in this PR.

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[codecov]

Codecov Report

Merging #1138 (96e2c85) into main (1c6378d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1138   +/-   ##
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  Coverage   82.09%   82.09%           
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  Files          56       56           
  Lines        1687     1687           
  Branches      462      462           
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  Hits         1385     1385           
  Misses        176      176           
  Partials      126      126           

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[semoal]

Looks perfect Michael, really happy to introduce this merge request to main :) Hope you get more users since we collaborate together =)

[MichaelHoste]

Thanks a lot for merging the PR @semoal !

Hope you get more users since we collaborate together =)

I sincerely hope so 😄