The biggest hold-up was missing fields (`premium_tier`,
`welcome_screen`, etc.) but it looks like someone has provided a
helpful function called `createGuild(...)` to provide sensible default
values.

This commit fixes the errors related to creating a guild from a
template. I've also refactored the code to include roles and channels in
the template.

To make sure that the @everyone role is cloned correctly, when
creating the guild from a template, we check if the role's ID
matches the template's `source_guild_id`. If it does, we set the
@everyone role to the new guild's ID.

The previous PATCH implementation was creating a new template rather
than editing the existing template. This resulted in all requests
failing because it was missing more than one required field.

Resolves: #1281

This reverts commit 69ea71a, reversing
changes made to 8b2faf0.

* Add eslint, switch to lint-staged for precommit

* Fix all ESLint errors

* Update GH workflow to check prettier and eslint

* Add script to automatically add license to each file

* Add license preamble to each file.

* Fix existing preamble detection breaking due to line endings. Git :(

* Prevent license from being added to code with other licenses