Implement triangulate algorithm for simple polygon

[ShampooDeng]

More detail can be found in https://en.wikipedia.org/wiki/Polygon_triangulation

• [x] check vertex type
• [x] handle start vertex
• [x] handle end veretx
• [x] handle split vertex
• [x] handle merge vertex
• [x] handle regualr vretex
• [x] monotone polygon output
• [x] monotone polygon triangulation
• [ ] ~validate if a polygon is monotone~

[ShampooDeng]

Blocked bt #5

[ShampooDeng]

Blocked by #5

5 is now partialy done.

[ShampooDeng]

Complete vertex type check with a48f7819453460235d3e8543363ef9492602bb88

[ShampooDeng]

implement monotone polygon partition with f8fa70ac3da2c057f52a8fd782a5d3fa1bd4f1cd

[ShampooDeng]

Implement monotone triangulation with 0e1cf8935c4df6e7171bdf0f693aaa07d8c4f7af