Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- .github/ISSUE_TEMPLATE/bug_report.md
  Took our version.
- CONTRIBUTING.md
  Updated the embedded copy of upstream's version.
- README.md
  Took our version.
- app/policies/status_policy.rb
  Not a real conflict, took code from both.
- app/views/layouts/embedded.html.haml
  Added upstream's changes (dns-prefetch) and fixed
  `%body.embed`
- app/views/settings/preferences/show.html.haml
  Reverted some of upstream changes, as we have a
  page dedicated for flavours and skins.
- config/initializers/content_security_policy.rb
  Kept our version of the CSP.
- config/initializers/doorkeeper.rb
  Not a real conflict, took code from both.

config/locales/pt-BR.yml

@@ -334,9 +334,7 @@ pt-BR:
       reported_by: Denunciada por
       resolved: Resolvido
       resolved_msg: Denúncia resolvida com sucesso!
-      silence_account: Silenciar conta
       status: Status
-      suspend_account: Suspender conta
       title: Denúncias
       unassign: Desatribuir
       unresolved: Não resolvido