Document compatibility guarantees

This falls under the umbrella of https://github.com/eclipse-iceoryx/iceoryx2/issues/450, but one specific piece of information I couldn't find anywhere is what guarantees Iceoryx2 makes regarding protocol stability across versions, which is important for making decisions about how and where we can use Iceoryx2. If I build two applications with two different versions of each other, should I expect them to be able to communicate with each other, assuming one isn't using a new feature not supported by the other? If so, will you ever make breaking changes and how will these correspond with release version numbers?

Start with umbrella issue #450 and search the repository documentation for existing versioning or protocol-stability guidance. Document whether applications built with different Iceoryx2 versions can communicate, how unsupported features affect compatibility, and how any breaking changes map to release version numbers.

Written by the indexing model from the issue text.