Merge tag 'v3.0.0' into glitch-soc/merge-upstream

diff --cc Gemfile.lock
Simple merge

diff --cc app/javascript/mastodon/locales/ja.json
Simple merge

diff --cc config/locales/en.yml
Simple merge

diff --cc config/locales/ja.yml
Simple merge

diff --cc lib/mastodon/version.rb
Simple merge