topbar with product dropdown

[nkylstad]

Added a product dropdown to the topbar, which contains links to the product pages. Currently contains the following products:

• Studio
• Authorization
• Broker
• Correspondence

Also added back the community link to the topbar, as there is now space for it.

https://github.com/Altinn/altinn-studio-docs/assets/1636323/a967f625-3ea6-4145-b54f-7445ab4e495c