Add missing globals dictionary to schema

[marcelldls]

For the globals dictionary, this still allows additionalProperties to be added - which means that you could accidentally include "enable" rather than "enabled" for example. However, since globals are passed to subcharts - there may be legitimate arbitrary globals passed that we have not considered. Im open to adding "additionalProperties": false because it would give a better hint during validation, but opting out of CI would be needed for adding arbitrary globals