Add first implementation of spanish language translation/localization

[luiscarlos2000]

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[trssharp]

Thanks Luis — the Spanish translation itself looks complete and useful.

I did not merge this PR as-is because the files landed at the repository root (nvda.po / nvda.mo). NVDA only loads add-on translations from locale/<language>/LC_MESSAGES/nvda.mo inside the packaged add-on, so root files would not actually appear when NVDA is set to Spanish.

I installed your catalog in the correct path on main via #11, credited you as last translator, and compiled the MO from there. After the next ClassicSpeech add-on install, Spanish NVDA should pick these strings up.

For later updates, please edit locale/es/LC_MESSAGES/nvda.po rather than adding files at the repo root. Poedit is still the right tool.

Closing this PR in favor of #11. Really appreciate the full 352-string pass.