[doc] Update maven artifacts for units and apriltags (NFC) (wpilibsuite#6123)

Author: sciencewhiz

MavenArtifacts.md

@@ -145,13 +145,19 @@ All artifacts are based at `edu.wpi.first.artifactname` in the repository.
   * wpinet
   * wpiutil
 
+* wpiunits
+
+* apriltag
+  * wpiutil
+  * wpimath
 
 ### Third Party Artifacts
 
 This repository provides the builds of the following third party software.
 
 All artifacts are based at `edu.wpi.first.thirdparty.frcYEAR` in the repository.
 
+* apriltaglib
 * googletest
 * imgui
 * opencv