edgegapcolor for Patches

Patch now supports an edgegapcolor parameter, similar to the existing gapcolor in Line2D. This allows patches with dashed edges to display a secondary color in the gaps, creating a "striped" edge effect.

This is useful when drawing unfilled patches on backgrounds of unknown color, where alternating edge colors ensure the patch boundary remains visible.

import matplotlib.pyplot as plt
from matplotlib.patches import Rectangle

fig, ax = plt.subplots()
rect = Rectangle((0.1, 0.1), 0.6, 0.6, fill=False,
                  edgecolor='orange', edgegapcolor='blue',
                  linestyle='--', linewidth=3)
ax.add_patch(rect)
plt.show()

(Source code, 2x.png, png)