Enable htmlzip downloads from readthedocs builds?

[abidsikder]

Is your feature request related to a problem?

An llms.txt for xarray does not exist so I am creating one. I am hoping to use the htmlzip download from readthedocs builds (like how zarr has available, image below) to collect together the auto generated api documentation.

Describe the solution you'd like

Enabling the htmlzip download on readthedocs builds.

This is a link to the readthedocs documentation on the option:
https://docs.readthedocs.com/platform/stable/downloadable-documentation.html

Describe alternatives you've considered

Scraping readthedocs is possible but I'd rather avoid it as it is error prone and fragile.

Additional context

No response

[welcome]

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[shoyer]

I enabled this in #10815. Let us know how if this works out for you!