Tangent on Path node unclear output

The « Tangent on Path » node returns an angle in degrees clockwise from the +X axis. However this is really not clear. The tooltip states:
> Determines the angle of the tangent at a point on the path, given by its progression from 0 to 1 along the path.
> If multiple subpaths make up the path, the whole number part of the progression value selects the subpath and the decimal part determines the position along it.

The angle of the tangent of a bézier curve is often expressed as a unit vector [such as on Pomax's bezierinfo](https://pomax.github.io/bezierinfo/#pointvectors). It is very easy for a user to assume that this might be the case (I did). This is especially true since non connected nodes do not get type hints about the output type. It is also possible that they do not know from where the angle is measured since it is never stated. Also why clockwise? I generally see anticlockwise from +X in e.g. argument of complex number.

Find the Tangent on Path node and its tooltip text, then verify how the node exposes its angle output. Clarify that the result is an angle in degrees, state that it is measured clockwise from the +X axis, and distinguish it from a unit-vector output. Done when the tooltip removes these ambiguities without changing node behavior.

Scritto dal modello di indicizzazione a partire dal testo della issue.