feat(benches): add a criterion bench for triangulation functions

[imrn99]

• add a single benchmark group, where exec time of both fan_cell and ear_clip is measured
• add a sample mesh file for the bench. the mesh is made up of both tris and quads

the sample vtk file is way too small to provide an interesting benchmark, but that way the benches will run without errors & on a mesh that isn't already full of tris

[imrn99]

ok maybe the 21K lines vtk file is a bad idea

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 82.62%. Comparing base (6236f8e) to head (d0a5f7b). Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #207 +/- ## ========================================== + Coverage 82.12% 82.62% +0.49% ========================================== Files 41 41 Lines 5650 5870 +220 ========================================== + Hits 4640 4850 +210 - Misses 1010 1020 +10 ```

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