refactor: Deprecate Formatter class

[Jiralite]

Please describe the changes this PR makes and why it should be merged:
Everything in this class is already exported at the top level. This just leads to code duplication.

• Some string types have been updated to Snowflake types
• Optional parameters were properly documented
• Documented all the methods as top-level functions. Previously, they weren't documented
• Removed TimestampStylesString from the class in the typings. It didn't even exist!
• Deprecated the class (with emitted warnings)

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

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Name	Status	Preview	Updated
discord-js	✅ Ready (Inspect)	Visit Preview	Jul 27, 2022 at 11:05AM (UTC)