Improve the editor

Summary: Improve the exhibition editor

Description:

• Override the pre-set Blocknote colors and add custom colors to fon and background, make sure to have light fonts also
• Add font selection options
• Make the content editor have the same background color as the exhibition
• Add blocks that can be added side by side, like columns, like here
• Make the blocknote commands menu be higher up when the user is at the bottom of the page, in some cases the commands menu is too small because it is cut off at the bottom

Acceptance Criteria:

• All the listed functionalities are added
• Everything is tested and works for different devices