Bug: turf/difference fails on a shared edge

It appears difference is failing due to a bug in a supporting library: https://github.com/w8r/martinez/issues/35

Here is a runnable test that exhibits the behavior

const difference = require('@turf/difference');
tape('Difference failure', (t) => {
  const polygon1 = {
    'type': 'Polygon',
    'coordinates': [
      [[ 10, 10 ], [ 80, 10 ], [ 80, 80 ], [ 10, 80 ], [ 10, 10 ]]
    ]
  };

  const polygon2 = {
    'type': 'Polygon',
    'coordinates': [
      [[ 20, 10 ], [ 30, 10 ], [ 30, 80 ], [ 20, 80 ], [ 20, 10 ]]
    ]
  };

  const result = difference(polygon1, polygon2);
});
// Expected result to be a multi-polygon
// Actual fails with exception `Each LinearRing of a Polygon must have 4 or more Positions.`

This failure happens since martinez returns a malformed polygon when two edges overlap. It returns a “good” difference and as well as a two- or three-point polygon. Could this be detected and handled prior to handing off to helper.polygon, which is where the exception occurs?

(Hoping creating a tracking issue between the two libraries helps find a common solution faster.)

[w8r]

linking the issue here w8r/martinez#81

[rowanwins]

Resolved in v6.2.0 onwards