chore(npm): use camunda nexus to proxy npm registry

related to #CAM-2971
fix(ie): correct the paths to bettre-dom polyfills

Related to: CAM-2808
 chore(release): Prepare release: set version to 7.2.0-alpha6
 chore(release): Prepare next development version: 7.2.0-SNAPSHOT
 chore(release): Prepare release: set version to 7.2.0
 chore(release): Prepare next development version: 7.3.0-SNAPSHOT