Add a NEWS file

What about collecting interesting changes in a NEWS file like

What about adding a NEWS file that gets short entries like:

* HdyLeaflet: new property `mode-transition-running`

This would

make it release notes more interesting since we could just c'n'p
users tracking the library have a place to check for changes and incompatiblities besides the git log

Entries should be short and part of the series that implements/changes a feature/API.

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