Closes: #2054

Closes: #2116

This restores commit 4ae029fc83bc38c4f79370c7bccaf38e30e342d6 from
git.xiph.org.

This restores commit f7c7db03f7cc00f75a273cbaa90321a5b68cb199 from
git.xiph.org.

Clean up/update homepage while here.

1.0.0 is a big release:
- 278 commits
- 174 files changed
- 12245 insertions(+)
- 11567 deletions(-)

This is restored commit ec2dacdd0414de36b48d1b90f40e2ffd0c7adc86 from
git.xiph.org.

Will be reapplied as applicable after restoring lost commits.

Build the static site on a continuous integration runner.
This provides both testing feedback on changes and simplifies
deployment.

Copied from the opus-website repository.

Just the plain copy of the docs from the repo for now, no
fancy markdown docs.

It was removed in newer jekyll versions.