Reference beta by version rather than date

Mention the other form of rollup merge for revert

Website lateral menu doesn't load without javaScript

Lang team process docs have both duplicated bits w/ lang-team and also disjoint bits

Compiler team lacks onboarding guide for new team members (and new maintainers)

landing page is very outdated

"Community" section is very outdated

release/process.html has a broken link

Mention versioned rustup-init binary URLs

triagebot autolabel: document interaction between trigger_* and exclude_labels