Updated README to show configurable env variables and their defaults

Author: CalebMorris

README.md

@@ -7,3 +7,21 @@ This bot requires the `Manage Messages` permission to control reactions. To gran
 `https://discordapp.com/oauth2/authorize?&client_id=<CLID>&scope=bot&permissions=8192`
 
 Alternatively, invoke `!wobabout` to get an invite link.
+
+## Configuration
+
+Additional environment variables can be used to configure the bot's various aspects.
+
+| Name | Default | What? |
+| ---- | ------- | ----- |
+| DISCORD_TOKEN | n/a; Required variable | Discord token to connect to the bot |
+| ARCANUM_TOKEN | | Token for unlimited API calls to the archive |
+| BRANDONSANDERSON_URL | | The homepage URL to extract progress information |
+| ARCANUM_URL | https://wob.coppermind.net | The base URL for API interactions |
+| WIKI_URL | coppermind.net | The wiki URL |
+| WIKI_COMMAND | coppermind|cm | The wiki interaction command |
+| WOB_COMMAND | wob | The WoB interaction command |
+| ARCANUM_ICON | ![](https://cdn.discordapp.com/emojis/373082865073913859.png?v=1) | The URL of the Icon to use for archive responses |
+| WIKI_ICON | ![](https://cdn.discordapp.com/emojis/432391749550342145.png?v=1) | The URL of the Icon to use for wiki responses |
+| ARCANUM_COLOR | ![#003A52](https://via.placeholder.com/15/003A52/000000?text=+) | The color to use in the WoB interactions |
+| WIKI_COLOR | ![#CB6D51](https://via.placeholder.com/15/CB6D51/000000?text=+) | The color to use in the Wiki interactions |