Statistics and graph in SingingResultsScene

[achimmihca]

Actual behaviour

The SingingResultsScene UI has been migrated to UIToolkit with #268.
It now shows the basic score information.

Expected behaviour

Further statistics and a graph could be shown (on demand, not by default).
The graph shows where in the song a player has lost points ("score at that time" vs. "possible score at that time").
Other statistics could include how many missed and good notes a player has sung.

[achimmihca]

There are some chart libs for Unity on GitHub, e.g., https://github.com/noirb/UIT_Charts