website: improve widgets

[casperdcl]

Changes

• docs: use pre-release theme (https://github.com/pydata/pydata-sphinx-theme/pull/1795)
• website: allow more than 3 "widgets" (multi-column cards)
• website: move content above "widgets"

Testing you performed

before	after (example)

Related issues/links

Fixes #1815

Checklist

• [x] I have performed a self-review of my code
• [x] ~I have added docstrings in line with the guidance in the developer guide~
• [x] ~I have updated the relevant documentation~
• [x] ~I have implemented unit tests that cover any new or modified functionality~
• [x] ~CHANGELOG.md has been updated with any functionality change~
• [x] Request review from all relevant developers
• [x] Change pull request label to 'Waiting for review'

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

• [x] The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License
• [x] I confirm that the contribution does not violate any intellectual property rights of third parties