Addition of categories and subcategories for landing pages standard on standaardenregister

[jitsedc]

Is your feature request related to a problem? Please describe.
As OSLO data standards have matured, more and more additional documentation needs to be added to the registry of standards to give a complete picture of the standard and its accompanying documentation.

Describe the solution you'd like
It would be good to add more categories under aanvullende documentatie to say for example

• Herbruikte standaarden (to give the link of reused standards to show reuse)
• Relevante vocabularia (to display Vocabularies that are tied closely together with an application profile or to display the 'parent' vocabulary when the vocabulary is meant as supplementary)
• Relevante applicatieprofielen (to display other application profiles based on the same vocabulary or application profiles that fall under the same domain).
• Implementaties en implementatiemodellen van deze standaard (to show implementation models that don't necessarily fall under the governance of OSLO and to show implementations themselves higlighting practical usage of the standards)
• Archief (application profiles or vocabularies that have been deprecated but should be kept somewhere for a matter of completeness)
• Charter (this category is already present in the JSON file but is displayed together with the other documentation in the HTML render)
• Datavoorbeelden (to give data examples that help implementers to reuse the standard if there are data examples that have been created for the specific standard)

Evidently they would only need to show up when used and it should probably still be possible to just have it on the level of 'documentation' without needing to use the subcategories.