Declaration based edit component, validation and playground - #64

Changed pages include:

• about.html - view
• edit-playground.html - view
• editorial-stance.html - view
• how-it-works.html - view
• imprint.html - view
• ar/about.html - view
• ar/editorial-stance.html - view
• ar/how-it-works.html - view
• ar/imprint.html - view
• bg/about.html - view

There are more changes not included in the list