Add translations to project's websites

[trallard]

📝 Summary

Follows #11
Add translations into three or more widely used languages (such as Spanish, Chinese, Japanese) to the website of at least eight core projects.

🚀 Tasks / Deliverables

• Define target translation languages for each project
• Add translations to each of the projects for all the target languages

📅 Estimated completion

12 months milestone

📋 Additional information

[rgommers]

Add translations into three or more widely used languages (such as Spanish, Chinese, Japanese) to the website of at least eight core projects.

It looks like we're at 6 sets of completed translations, and 2 being deployed now: numpy.org updates and scipy.org new translations?

[melissawm]

• For pandas, we are missing some feedback on this PR: ENH: Create infrastructure for translations pandas-dev/pandas#61220
• For zarr, there is a PR here: Add language switcher zarr-developers/zarr-developers.github.io#144
• For networkx, there is a PR here: Add language switcher networkx/website#25