Add Nextcloud 21 support

… and only use php7.2 for stable20

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Document the mail.app.verify-tls-peer setting

Fix avatar threading

Signed-off-by: GretaD <gretadoci@gmail.com>

Signed-off-by: Cyrille Bollu <cyrpub@bollu.be>

Switch to style-loader

Signed-off-by: Julius Härtl <jus@bitgrid.net>

Use absolute URLs on search

Signed-off-by: Joas Schilling <coding@schilljs.com>

Bumps [css-loader](https://github.com/webpack-contrib/css-loader) from 3.6.0 to 4.3.0.
- [Release notes](https://github.com/webpack-contrib/css-loader/releases)
- [Changelog](https://github.com/webpack-contrib/css-loader/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack-contrib/css-loader/compare/v3.6.0...v4.3.0

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@vue/test-utils](https://github.com/vuejs/vue-test-utils/tree/HEAD/packages/test-utils) from 1.0.4 to 1.1.0.
- [Release notes](https://github.com/vuejs/vue-test-utils/releases)
- [Changelog](https://github.com/vuejs/vue-test-utils/blob/dev/packages/test-utils/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vue-test-utils/commits/v1.1.0/packages/test-utils

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [webpack-node-externals](https://github.com/liady/webpack-node-externals) from 1.7.2 to 2.5.2.
- [Release notes](https://github.com/liady/webpack-node-externals/releases)
- [Commits](https://github.com/liady/webpack-node-externals/compare/v1.7.2...v2.5.2

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [file-loader](https://github.com/webpack-contrib/file-loader) from 6.0.0 to 6.1.0.
- [Release notes](https://github.com/webpack-contrib/file-loader/releases)
- [Changelog](https://github.com/webpack-contrib/file-loader/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack-contrib/file-loader/compare/v6.0.0...v6.1.0

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Bumps [@nextcloud/l10n](https://github.com/nextcloud/nextcloud-l10n) from 1.4.0 to 1.4.1.
- [Release notes](https://github.com/nextcloud/nextcloud-l10n/releases)
- [Changelog](https://github.com/nextcloud/nextcloud-l10n/blob/master/CHANGELOG.md)
- [Commits](https://github.com/nextcloud/nextcloud-l10n/compare/v1.4.0...v1.4.1

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

MailboxPicker

Signed-off-by: Holger Dehnhardt <holger@dehnhardt.org>

Fix shortkey

Signed-off-by: GretaD <gretadoci@gmail.com>

Make it possible to view messages of the same thread directly

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Revert "Bump css-loader from 3.6.0 to 4.2.2"

Bump @nextcloud/dialogs from 1.4.0 to 2.0.1

Fix message source scrol bar