Feat: Lazy Load Design Library module

[bfintal]

Change the implementation of the Design Library:

• Remove the Design Library block, instead we register the Design Library as a Plugin instead (tentative, you can change this during implementation)
• Lazy load the design library module so all related files will be split into a separate chunk and will only be loaded when the design library button is going to be used

Goal:

• design library will not be loaded at the start
• design library will not be included in stk.js