Handle extra closing segments

[snoyer]

svgpathtools will sometime add short line segments to close paths. This seems to mostly happen with relative paths (I assume through error accumulation). In this PR:

• we try and avoid the situation internally by using absolute path strings when converting from svgpathelements to svgpathtools paths
• we check for these extra closing segments when generating edges

[codecov-commenter]

Codecov Report

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

Comparison is base (fc5bef7) 98.96% compared to head (d4cbde0) 98.98%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #16 +/- ## ========================================== + Coverage 98.96% 98.98% +0.01% ========================================== Files 8 8 Lines 1065 1086 +21 ========================================== + Hits 1054 1075 +21 Misses 11 11 ``` | [Files](https://app.codecov.io/gh/snoyer/ocpsvg/pull/16?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [ocpsvg/ocp.py](https://app.codecov.io/gh/snoyer/ocpsvg/pull/16?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-b2Nwc3ZnL29jcC5weQ==) | `97.71% <100.00%> (ø)` | | | [ocpsvg/svg.py](https://app.codecov.io/gh/snoyer/ocpsvg/pull/16?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-b2Nwc3ZnL3N2Zy5weQ==) | `98.23% <100.00%> (+0.05%)` | :arrow_up: | | [tests/test\_svg.py](https://app.codecov.io/gh/snoyer/ocpsvg/pull/16?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-dGVzdHMvdGVzdF9zdmcucHk=) | `100.00% <100.00%> (ø)` | |

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