Adding Test for Partial Regex Search at 0 Index

[gandersen101]

Adds a test to ensure that partial regex searching will match a token at the 0 index of a doc.

[codecov[bot]]

Codecov Report

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

Project coverage is 96.18%. Comparing base (01448ee) to head (7d3658c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #85 +/- ## ======================================= Coverage 96.18% 96.18% ======================================= Files 24 24 Lines 1206 1206 Branches 281 281 ======================================= Hits 1160 1160 Misses 31 31 Partials 15 15 ```

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