Version 2.1.18 - Support for Java 16 and Minecraft 1.17

[GiantTreeLP]

This pull request includes:

• [ ] breaking changes
• [x] no breaking changes (unless unstable or unused parts of CloudNet were used)

Changes made to the repository:

• Updated a few dependencies
• Fixed a few classes and made them compatible with Gson and Java 16
• Made compatible with Minecraft 1.17
• Fix documentation in such a manner that it produces no warnings

Documentation of test results:

See the build result. Minecraft 1.17 was working as well, reviewers should check that.

Related issues/discussions:

A few requests on discord asked for such an update.

This pull request also marks a new release.

Have fun!