Prepare 0.1.1

Now that Toolbx 0.1.0 has been released, it's a good time to revisit the
format of the release notes.

The release notes are now written in the past tense as suggested by the
Kubernetes guidelines [1].  They are broken down into different sections
to make it easier to understand the impact of the changes, with the
names of the sections loosely taken from projects like Flatpak [2].

[1] https://github.com/kubernetes/community/blob/master/contributors/guide/release-notes.md

[2] https://github.com/flatpak/flatpak/blob/main/NEWS

#1581