Allow mapping of emoticons to emojis

[ldilley]

Add a boolean configuration option to terracord.xml that toggles the mapping of emoticons to emojis. If the option is set to true, load additional configuration that contains mappings of emoticons to emojis. The new configuration data will contain key-value pairs and can be customized. When the option is enabled, Discord messages containing a mapped emoticon from Terraria players will instead display the equivalent emoji.

The new terracord.xml option will be:

<map emoticons="true" />

The mappings can be added to the existing configuration file in a new section called <emomap>. They might look something like:

<emomap>
<emo key=":)" value=":slight_smile:" />
<emo key=":(" value=":slight_frown:" />
<emo key="&lt;3" value=":heart:" />
</emomap>