Update CHANGELOG.md

[ue71603]

This is the PR to update the changelog.

[ue71603]

@trurlurl Some of the changes should be moved to the category "Breaking", we can also do this later.

[ue71603]

@trurlurl The headings should perhaps a bit changed. I think new service/added/changed/removed would be the titles. The distinction between 1.1 and 2.0 can be removed (as we only have 2.0). We should mark changes as breaking, when formerly valid examples are no longer valid:

• changes of element names
• changes of structure that are not compatible
• optional elements that are now mandatory
• enum values removed/altered
• type of an element changed (more restrictive/incompatible alteration). Perhaps we should mark each such line with "[breaking]". What do you think?

Otherwise I think this is working out fine.

[ue71603]

@trurlurl you say, when we are ready to review and merge?

[trurlurl]

We are ready, the list is complete & up to date.

[ue71603]

@trurlurl when you accept, we can merge it...