adding more docker usage examples with bot, small script to gather everything and list of options for the Cli

Docker-usage-instructions.md

@@ -1,3 +1,5 @@
+### Usage with session token and ID of channel
+
 To pull the latest version:
 
     $ docker pull tyrrrz/discordchatexporter
@@ -6,5 +8,66 @@ To export:
 
     $ docker run tyrrrz/discordchatexporter export -t TOKEN -c CHANNEL
 
+##
+
+### Usage with a bot instead of a session token
+
+To get list of guilds available to a bot:
+
+    $ docker run tyrrrz/discordchatexporter guilds -t TOKEN -b
+
+To get list of channel available to a bot on a given guild:
+
+    $ docker run tyrrrz/discordchatexporter channels -t TOKEN -b -g GUILD_ID
+
+To get content of channel:
+
+    $ docker run tyrrrz/discordchatexporter export -t TOKEN -b -c CHANNEL
+
+Export path is in /a in docker image, so if you need to bring the file on the host use the following command:
+
+    $ docker run -v $PWD:/a tyrrrz/discordchatexporter export -t TOKEN -b -c CHANNEL
+
+And finally a small script to gather every channel your bot is on:
+
+```bash
+MY_TOKEN_ID=<TOKEN ID HERE>
+
+# get list of guilds
+guilds=$(docker run --rm -v $PWD:/a tyrrrz/discordchatexporter guilds -t $MY_TOKEN_ID -b | tr -d '[:blank:]')
+
+for guild in $guilds; do
+  guild_id=$(echo $guild | cut -d '|' -f 1)
+  guild_name=$(echo $guild | cut -d '|' -f 2)
+  echo processing $guild_name with id $guild_id
+
+  channels=$(docker run --rm -v $PWD:/a tyrrrz/discordchatexporter channels -t $MY_TOKEN_ID -b -g $guild_id | tr -d '[:blank:]')
+  for channel in $channels; do
+    channel_id=$(echo $channel | cut -d '|' -f 1)
+    channel_name=$(echo $channel | cut -d '|' -f 2)
+
+    echo processing $channel_name in guild $guild_name with channel id:  $channel_id
+    result=$(docker run --rm -v $PWD:/a tyrrrz/discordchatexporter export -t $MY_TOKEN_ID -b -c $channel_id -o /a/${guild_name}_${channel_name}.html)
+    if [ ! $? ]; then
+      echo an error happenned: $result
+      exit 1
+    else
+      echo channel saved as ${guild_name}_${channel_name}.html
+    fi
+  done
+done
+```
+
+List of options for cli call from [ExportChatOption.cs](https://github.com/Tyrrrz/DiscordChatExporter/blob/master/DiscordChatExporter.Cli/Verbs/Options/ExportChatOptions.cs):
+
+    -c|--channel <channel_id>
+    [-f|--format] <PlainText|HtmlDark|HtmlLight|Csv>
+    [-o|--ouptput] <path to output file>
+    [--after] <limit export to messages after this date>
+    [--before] <limit export to messages before this date>
+    [-p|--partition] <split output by this amount of messages>
+    [--dateformat] <date format>
+    [--grouplimit] <messages group limit>
+
 ##
 Credits to [@simnalamburt](https://github.com/simnalamburt)