Kerbal Joint Reinforcement v3.7.4 for KSP 1.12.x

What's Changed

• Fix inter-vessel joints getting created on decoupling by @siimav in #16

Other non-user-facing code changes

• KJRMultiJointManager is no longer a singleton
• Do not add duplicate joints to KJRMultiJointManager dictionary
• Use stock method for determining if part is a decoupler
• Add GH action that uploads build artifacts to PRs
• Use stock method for finding launch clamps
• Clean up temp lists in KJRMultiJointManager after finishing joint updates

Full Changelog: v3.7.3.0...v3.7.4.0