Add a version number (and a changelog?)

[Binnette]

Hi, can you please add a version number to your app and display it and the web interface.

This number can help to track which version of osm-wikidata was used to create a changeset. And will allow us, to follow possible regression between versions.

If you can also, write a "CHANGELOG", it can be create for users to follow new features and bug fixes.

Have a nice day 👍