tempo (metronome) marks with approximation sign

If you want to display an approximation sign in your (numeric) tempo marks, or if you want to display the tempo number in a different color, or if you want to hide the parenthesis in your combined tempo mark (both name and number), this example demonstrates how the translation functions found in .../scm/translation-functions.scm can be adopted, doing it in a tuneable way with new optional context properties.