Bump to livechart-2

[danirabbit]

For the GTK4 break, we should bump the version number to 2.0 and the library to livechart-2 so that it can be installed side-by-side with livechart 1.x

[stsdc]

Do we need anything else to publish livechart-2, besides #4?

[danirabbit]

Tagged 2.0 :)