✨ Purge configuration data of removed guilds

[n1ckoates]

When Needle is removed from a guild (kicked, guild deleted, etc.), it will now delete the configuration data of that guild.

On startup, Needle will compare the configs directory to its current guilds, deleting ones it's no longer in. This is done in case Needle is offline when the guildDelete event fires. As a precautionary measure, Needle will not delete configs if no guilds are present; this protects against the wrong token being used by mistake, or a theoretical Discord API error.

Both of these things are achieved through the resetConfigToDefault function, which just deletes the respective file.

• Closes 💡 Purge configuration data of removed guilds #36

[n1ckoates]

If this pull request is merged & I become a contributor, I'm fine with the proposed AGPL license change.

[c43721]

If #34 gets merged before this, you're going to have merge conflicts FYI.

[MarcusOtter]

Thank you so much, it works flawlessly ✨

I moved the function to configHelpers.ts where we already have access to the CONFIGS_PATH and fs. It keeps index.ts more tidy as well. Other than that I just did some tiny nitpicks like making variable names slightly more descriptive (e.g. files => configFiles) and moved the logging of Deleted config for guild ${id} to the actual reset command.

Thank you for this! 🎉