Release camunda-modeler v5.15.1

[philippfromme]

What's inside?

• FIX: fix element templates and plugins not found error on Windows (#3863)

Release Checklist

To be done immediately after creating this issue.

• add Slack role to release manager (@modeling-release-manager)

To be done to prepare and build the release.

• make sure changes in upstream libraries are merged and released
  • bpmn-js, dmn-js, *-properties-panel, *-moddle, camunda-bpmn-js, form-js, ...
• make sure dependencies to upstream libraries are updated and can be installed (rm -rf node_modules && npm i && npm run all works)
• close all issues which are solved by dependency updates
• smoke test to verify all diagrams can be created
• update Release Info
• update CHANGELOG
• create release (npm run release), cf. release schema
  • wait for release build to create the artifacts
• prepare a list of what was changed or needs to be tested
• execute integration test, verifying fixed things are actually fixed
• (optional) trigger QA for testing

To be done to make the release publicly available.

• publish release on Github Releases
• trigger downloads page update via marketing request form
• add new version to update server releases
• publish release via update server (push to live)