Add a Zenodo DOI to the README

[codecov[bot]]

Codecov Report

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

Comparison is base (8b6f61f) 95.62% compared to head (9b7d857) 95.62%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #955 +/- ## ======================================= Coverage 95.62% 95.62% ======================================= Files 126 126 Lines 7355 7355 Branches 512 512 ======================================= Hits 7033 7033 Misses 322 322 ``` | [Flag](https://app.codecov.io/gh/fulcrumgenomics/fgbio/pull/955/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fulcrumgenomics) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/fulcrumgenomics/fgbio/pull/955/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fulcrumgenomics) | `95.62% <ø> (ø)` | | 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=fulcrumgenomics#carryforward-flags-in-the-pull-request-comment) to find out more.

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