Add example projects

[ConorOkus]

Similar to - https://lightningdevkit.org/examples/

[ConorOkus]

Karavan - https://github.com/notmandatory/karavan
Devkit-wallet - https://github.com/notmandatory/karavan
Padawan-wallet - https://github.com/thunderbiscuit/padawan-wallet

[thunderbiscuit]

The new case studies page fulfills that role now! We're also removing the examples/ endpoint, because it was cross-referencing things in the case studies page without a clear separate purpose.