Added support for more options & slash template

[Fusezion]

Handler Changes

While I was fixing the typo with IntChoices I remembered there are other options we're missing like "Boolean", "Mentionable", and "Number". This pull request aims to add support for both Boolean and Number while adding mentionable was easy it just didn't seem worth it as it'll only combine both user and roles leaving it obsolete in some things.

Template.JS File

Something that was always killing me when learning slash commands, was the fact we didn't have any template file for seeing everything as it was mostly in every file being reused. I've created a new file under SlashCommands for a "normal" slash command and added the new options and made it less of a mess when learning,