Adding option to specify custom model root

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.46%. Comparing base (f6fc65e) to head (a1ac7ae). Report is 1 commits behind head on main.

Files	Patch %	Lines
buzz/model_loader.py	83.33%	1 Missing :warning:
buzz/transcriber/recording_transcriber.py	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #894 +/- ## ========================================== - Coverage 82.49% 82.46% -0.03% ========================================== Files 85 85 Lines 4684 4682 -2 ========================================== - Hits 3864 3861 -3 - Misses 820 821 +1 ``` | [Flag](https://app.codecov.io/gh/chidiwilliams/buzz/pull/894/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/894/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams) | `82.16% <75.00%> (+0.01%)` | :arrow_up: | | [macOS](https://app.codecov.io/gh/chidiwilliams/buzz/pull/894/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Chidi+Williams) | `82.33% <75.00%> (-0.03%)` | :arrow_down: | 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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