Add semantic version type

[jbkroner]

Adding a semantic version type as requested in #2506 in the pydantic repo.

The implementation here is just the example from the python-semver docs + some additional tests.

When this PR gets a thumbs up I will update the docs in python-semver.

Any feedback appreciated, cheers.

edit: tracking on coverage and 3.8 compatibility issues, will try to get that covered early this week before marking as ready for review.

Selected Reviewer: @yezz123

[codecov[bot]]

Codecov Report

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

Project coverage is 100.00%. Comparing base (e186814) to head (563284f). Report is 38 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #199 +/- ## ========================================== Coverage 100.00% 100.00% ========================================== Files 11 17 +6 Lines 685 960 +275 Branches 169 232 +63 ========================================== + Hits 685 960 +275 ```

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[jbkroner]

please review

[jbkroner]

@yezz123 fixes applied. apologies for the extra commits - didn't click that I could run the linter / pre-commit stuff locally (duh) following the instructions in the main pydantic repo.

[yezz123]

@yezz123 fixes applied. apologies for the extra commits - didn't click that I could run the linter / pre-commit stuff locally (duh) following the instructions in the main pydantic repo.

No Problem now we have it ready we can merge it, Thanks for the great work @jbkroner 🚀