Add `Progressive Sovereignty` principle to `Principles` page

[Bosch-0]

A principle we should have for the guide, and already do in many ways, is the idea of designing Bitcoin applications to be Progressively sovereign

What is a progressively sovereign bitcoin application?

To put it simply, it's making flexible bitcoin applications that allow users to become more sovereign with their bitcoin and data when they are ready to do so.

An example is Breez: It is a pretty basic wallet initially but if users want to they can minimize their trust from Breez the LSP and connect to their own Neutrino node and (coming soon) connect to different LSPs.

Could even take this a step further and allow the wallet to be a Lightning node remote (like Zeus) if the user wants to do that. We are planning on attempting to 'gamify' this process of making users more sovereign once Zeus has mobile node functionality.

We should instill this principle throughout the guide and ensure users aren't getting put in a walled garden that may over time slowly erode their sovereignty over their bitcoin.

[GBKS]

Isn't that already covered in Interoperability?

[Bosch-0]

I don't see them the same, this is more focused on having the option to go advanced from basic if the user wants to. I guess there is some overlap but I'd say they are quite different.

[pavlenex]

We now do mention a briefly of both in Self-custody and Security.

If you feel we can add more, let's revisit and re-open the issue.