Help, messages, better parsing, packaging

Add help message, add support for attaching a message to a reminder, use
a better crate for parsing durations, add debian packaging.

debian/am-reminder-bot.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=Matrix reminder bot
+After=network.target
+
+[Service]
+ExecStart=/usr/bin/am-reminder-bot
+Environment="SESSION_FILE=/etc/am-reminder-bot/session.json" "STORAGE_DIR=/var/lib/am-reminder-bot/store"
+User=am-reminder-bot
+Group=am-reminder-bot
+
+[Install]
+WantedBy=multi-user.target

debian/copyright

@@ -0,0 +1,19 @@
+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Upstream-Name: Reminder bot
+Source: https://git.nao.sh/amanda/reminder-bot
+
+Files: *
+Copyright: 2021 Amanda Graven <amanda@amandag.net>
+License: EUPL-1.2
+Copyright 2021 Amanda Graven
+Licensed under the EUPL, Version 1.2 or – as soon they will be approved by the
+European Commission - subsequent versions of the EUPL (the "Licence"); You may
+not use this work except in compliance with the Licence. You may obtain a copy
+of the Licence at:
+.
+https://joinup.ec.europa.eu/software/page/eupl
+.
+Unless required by applicable law or agreed to in writing, software distributed
+under the Licence is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR
+CONDITIONS OF ANY KIND, either express or implied.  See the Licence for the
+specific language governing permissions and limitations under the Licence.

debian/postinst

@@ -0,0 +1,7 @@
+#!/bin/bash
+set -e
+
+adduser --quiet --system --group --home "/var/lib/am-reminder-bot" am-reminder-bot
+chown -R am-reminder-bot: /etc/am-reminder-bot
+
+#DEBHELPER#

debian/postrm

@@ -0,0 +1,2 @@
+#!/bin/bash
+#DEBHELPER#

debian/prerm

@@ -0,0 +1,2 @@
+#!/bin/bash
+#DEBHELPER#