Improve sampler docs

[cpfiffer]

The docs did not fully convey how to set temperature, and I figured I'd update the sampler docs more generally. A user was having issues with this in the Discord.

I update the documentation to include a few things:

Changes:

• Brief overview in layman's terms of what the samplers actually do
• How multinomial sampling works
• Added "Parameters" sections for beam search and multinomial sampling
• Added more headers to break up the various parameters in multinomial sampling
• Provided a simple comparison table to help users choose from the available samplers

Misc doc convenience stuff:

• gitignore for mkdocs-generated folders
• Manually triggered build/publish GitHub Actions for the docs