Update Dockerfile to install apprise

Fixes: #581

CHANGELOG.md

@@ -7,6 +7,7 @@ All notable changes to this project will be documented in this file.
 - Switch from croniter to cronsim (vendored in hc.lib.cronsim)
 - Change outgoing webhook timeout to 10s, but cap the total time to 20s
 - Implement automatic `api_ping` and `api_notification` pruning (#556)
+- Update Dockerfile to install apprise (#581)
 
 ### Bug Fixes
 - Fix hc.api.views.ping to handle non-utf8 data in request body (#574)

docker/Dockerfile

@@ -8,7 +8,7 @@ RUN \
     printf "[global]\nextra-index-url=https://www.piwheels.org/simple\n" > /etc/pip.conf ; \
     fi
 RUN pip wheel --wheel-dir /wheels -r /tmp/requirements.txt
-RUN rm -f /etc/pip.conf && pip wheel --wheel-dir /wheels uwsgi
+RUN rm -f /etc/pip.conf && pip wheel --wheel-dir /wheels apprise uwsgi
 
 FROM python:3.9-slim-buster