Allow user to create a "zeroed" reference on the compass widgets

The idea is that, the user having a physical reference to a direction (like the direction the computer/chair is pointed to), it would make the navigation easier if he could have the zero of the compass aligned with this direction, so the compass arrow would visually point in the same direction the vehicle is pointing to, physically.

The idea is not to substitute the true compass arrow, but to create a second one for that, in a different color.

Start by locating the compass widgets in the TypeScript/Vue project and read how the existing compass arrow is rendered and oriented. Determine how a user-set physical reference and a second differently colored arrow should be represented; done means the true compass arrow remains visible and the zeroed reference arrow tracks the chosen direction.

Written by the indexing model from the issue text.