Migrate site to Tailwind-styled Hugo Blox template

[carlosmalt]

Hugo Blox switched from Bootstrap-styled templates to Tailwind-styled ones. The old Bootstrap-styled templates tend to not support newer versions of Hugo. This might be why Hugo versions greater than 0.119.0 tend to throw errors when building this website.

This is not urgent but might mean more work the longer we wait.

[slieggi]

OK -- I'd like to wait until after the GSoC application process is over if possible.