Adding option to set n_threads for Whisper.cpp

[codecov[bot]]

Codecov Report

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

Project coverage is 82.48%. Comparing base (5d83950) to head (23e39b0). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #892 +/- ## ======================================= Coverage 82.48% 82.48% ======================================= Files 85 85 Lines 4681 4683 +2 ======================================= + Hits 3861 3863 +2 Misses 820 820 ``` | [Flag](https://app.codecov.io/gh/chidiwilliams/buzz/pull/892/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams) | Coverage Δ | | |---|---|---| | [Linux](https://app.codecov.io/gh/chidiwilliams/buzz/pull/892/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams) | `82.14% <100.00%> (-0.04%)` | :arrow_down: | | [macOS](https://app.codecov.io/gh/chidiwilliams/buzz/pull/892/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams) | `82.36% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams#carryforward-flags-in-the-pull-request-comment) to find out more.

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