Implement Confidence Argument Extension

[jonasthewolf]

• [x] Add rendering of nodes with ACP
• [x] Add rendering of edges with ACP
• [x] Add tests for deserialization
• [x] Add tests for validation checks
• [x] Add documentation for feature
  • [x] Extra section for Confidence Argument Extension
  • [x] Validation message
  • [x] Standard support

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 99.12664% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 98.65%. Comparing base (4a69806) to head (16dd7d1).

Files	Patch %	Lines
src/render.rs	93.02%	3 Missing :warning:
src/dirgraphsvg/nodes/mod.rs	98.21%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #409 +/- ## ========================================== + Coverage 98.61% 98.65% +0.04% ========================================== Files 21 22 +1 Lines 5038 5373 +335 ========================================== + Hits 4968 5301 +333 - Misses 70 72 +2 ```

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