feat: Add a mapper cookiecutter template

[pnadolny13]

Closes #1645

I was trying to build a mapper related to https://github.com/meltano/internal-data/issues/131 and noticed it was pretty difficult and manual. Creating at least a draft of this was going to save me time vs manually copy/pasting an existing mapper.

I wasnt sure what the cookiecutter.test.yml was actually doing, it looks like theyre outdated (e.g. include_cicd_sample_template vs what I think is now called include_ci_files). Let me know if I should put that back in.

I tried to update everything I could find but will manually test that it works as expected.

NOTE: the one thing thats not incorporated in here from map-gpt-embeddings is the time_extracted parsing, see https://github.com/MeltanoLabs/map-gpt-embeddings/blob/2de64bb8d5b42ffdb3b93420efd1d2bb06141d7b/map_gpt_embeddings/sdk_fixes/messages.py#L13. I used this cookiecutter and did see that error pop up but I had a hard time reproducing it. I will create a separate bug issue if I'm able to reproduce.

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📚 Documentation preview 📚: https://meltano-sdk--1892.org.readthedocs.build/en/1892/

[codecov]

Codecov Report

Merging #1892 (f0918cc) into main (6ce7eab) will not change coverage.
The diff coverage is n/a.

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[edgarrmondragon]

Nice! Thanks @pnadolny13.