Customize footer block

[ulyanas]

For STAKE Beacon Chain:

1. Remove column "Legal Notices"
2. Modify "Resources":
   Resources
   Overview
   Github
3. Remove "Links column" (all links moved to "Resources")
4. Remove copyright "©..."
5. Keep version and light/dark theme switcher

For Canary network:
Make the "Resources" block configurable.

[akolotov]

It seems a duplicate for #16