feat: aiken-based bet-ref example

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Summary

This PR shows the use of an Aiken-based contract for bet-ref example.

Type of Change

Please mark the relevant option(s) for your pull request:

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] Code refactoring (improving code quality without changing its behavior)
[ ] Documentation update (adding or updating documentation related to the project)

Checklist

Please ensure that your pull request meets the following criteria:

[x] I have read the Contributing Guide
[x] My code follows the project's coding style and best practices
[x] My code is appropriately commented and includes relevant documentation
[x] I have added tests to cover my changes
[x] All new and existing tests pass
[ ] I have updated the documentation, if necessary

Testing

To run unified tests with Aiken-based contract use the following command:

export AIKEN_BET_REF=1; cabal run atlas-unified-tests

geniusyield / atlas