Add source generation; move model and part definitions to yaml files

[coavins]

Description

This PR aims to improve the maintainability of models and parts by moving their definition to a single place and using a "build" step to generate certain source files which are currently scattered throughout the repo. This would do away with the need to maintain the Zomboid "item" and "repair" txt files, certain Lua files, and (possibly) the Zomboid translation files.

This PR also ought to introduce a Github Action to run the "build" step and generate a package or artifact which could be used for validation and ci.

Related Issues

Resolves #70

Checklist

• Code follows the project's coding standards.
• Documentation is updated (if applicable).
• All checks and tests pass locally.
• The commit messages follow the project's commit message conventions)

Additional Notes

A good followup task to this work would be to add a Github Action to (somehow) generate some nice markdown documentation from the schema files. Surely this must be possible. This would potentially address issue #42.

We could also add a Github Action that validates the model and part yaml files using these schemata.

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