Adding note on ffmpeg + fix for faster whisper on macOS

[codecov[bot]]

Codecov Report

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

Project coverage is 82.38%. Comparing base (ecb85ae) to head (32a7c43).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #882 +/- ## ========================================== + Coverage 82.37% 82.38% +0.01% ========================================== Files 85 85 Lines 4601 4604 +3 ========================================== + Hits 3790 3793 +3 Misses 811 811 ``` | [Flag](https://app.codecov.io/gh/chidiwilliams/buzz/pull/882/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/882/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams) | `82.03% <66.66%> (-0.02%)` | :arrow_down: | | [macOS](https://app.codecov.io/gh/chidiwilliams/buzz/pull/882/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams) | `82.12% <100.00%> (+0.53%)` | :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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