feat: server subscription tier manager and class

[Uhuh]

Please describe the changes this PR makes and why it should be merged: Created new class for users to consume the ServerSubscriptionTier and added a GlobalManager for the ServerSubscriptionTier that implements the basic read/readMany methods.

Status

• [ ] Code changes have been tested.

Semantic versioning classification:

• [x] This PR changes the library's interface (methods or parameters added)
• [ ] This PR includes breaking changes (methods removed or renamed, parameters moved or removed)
• [ ] This PR only includes non-code changes, like changes to documentation, README, etc.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 87e3becb68877ef1a5377bcbf0f5a5cae3d03b1e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

| Name | Type | | -------------- | ----- | | guilded.js | Minor | | @guildedjs/gil | Patch |

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