Merge #1338

1338: Add GPG to Roundcube r=mergify[bot] a=PhilRW

The web UI was complaining that it couldn't find the GPG binary. Turns out it wasn't installed.

## What type of PR?

bug fix

## What does this PR do?

Adds GPG binary to Roundcube

Co-authored-by: Philip Rosenberg-Watt <PhilRW@users.noreply.github.com>
Co-authored-by: Dario Ernst <github@kanojo.de>

webmails/roundcube/Dockerfile

@@ -23,6 +23,7 @@ ENV CARDDAV_URL https://github.com/blind-coder/rcmcarddav/releases/download/v3.0
 RUN apt-get update && apt-get install -y \
       zlib1g-dev libzip4 libzip-dev libpq-dev \
       python3-jinja2 \
+      gpg \
  && docker-php-ext-install zip pdo_mysql pdo_pgsql \
  && echo date.timezone=UTC > /usr/local/etc/php/conf.d/timezone.ini \
  && rm -rf /var/www/html/ \