Add .version file to track latest version

[ewanharris]

📝 Checklist

• [ ] All new/changed/fixed functionality is covered by tests (or N/A)
• [ ] I have added documentation for all new/changed functionality (or N/A)

🔧 Changes

📚 References

🔬 Testing

[codecov-commenter]

Codecov Report

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

Comparison is base (6cc5f8a) 95.98% compared to head (03f30f4) 95.98%. Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #246 +/- ## ======================================= Coverage 95.98% 95.98% ======================================= Files 7 7 Lines 324 324 ======================================= Hits 311 311 Misses 10 10 Partials 3 3 ```

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