security fix: update marked version

subdependency of openlayers had a vulnerability. This bug should not have affected users of the compiled scripts in dist. Updated openlayers, so a newer version of marked (0.3.7 -> 0.3.12) will be installed when nlmaps is installed from npmjs.com.

v2.2.0

New version of NL Maps library including:

• geocoder and geocoder control (address search bar) -- uses the PDOK LocatieServer
• ability to add a marker to the map
• ability to add overlay WM(T)S layers
• code cleanup, improved developer documentation and workflow
• the wizard now uses the nlmaps library

nlmaps@2.1.0

nlmaps@2.1.0