5.21.0

• [all] feat: Convert sentry-javascript to ESLint (#2786)
• [internal/eslint] feat: Add @sentry-internal/eslint-config-sdk (#2807)
• [internal/eslint] feat: Add @sentry-internal/eslint-plugin-sdk (#2807)
• [ember] feat: Add @sentry/ember (#2739)
• [angular] feat: Add @sentry/angular (#2787)
• [react] feat: Add routing instrumentation for React Router v4/v5 (#2780)
• [gatsby] feat: support process.env.SENTRY_RELEASE (#2776)
• [apm/tracing] feat: Export addExtensionMethods for SDKs to use (#2805)
• [apm/tracing] ref: Remove express typing (#2803)
• [node] fix: Retry-After header in node should be lower-case (#2779)