Fix ranges, fix #25 and support 1.21

[EnderKill98]

Hi,

this does the following changes:

• Adjusts the check, whether a NoteBlock is reachable, to account for both the old and new way. If a user is certain what version the server uses, they may configure what check to use in the mod settings.
• Addresses #25 with a new mod setting option as well.

These changes can make sense to release on its own for 1.20.5/6.

• Lastly, this updates the mod to 1.21 as well.

---

For anyone interested, here the jar files:

• 1.20.5/6 (all commits, until the one updating to 1.21): disc_jockey-1.5.0-rangestuff.zip
• All changes, for 1.21: disc_jockey-1.5.0-dev-1.21.zip