[svg-paths] Define normalised path

The spec should be more clear what is the output of path.getPathData({normalise: true});

I would propose to define the normalized path as a path that consists from zero or more subpaths where each subpath must start with "M" segment, followed by one or more "C" or "L" segments, optionally followed by "Z" segment.

From my experience paths normalised to this subset are the easiest to work with as you don't need to perform repetitive checks for special cases like multiple subsequent “M” segs.