Only run GH actions on pull requests

[jakejackson1]

Description

Switch to Codecov action.

Testing instructions

Automated tests

Screenshots

Checklist:

• [ ] I've tested the code.
• [ ] My code is easy to read, follow, and understand
• [ ] My code follows the accessibility standards.
• [ ] My code has proper inline documentation / docblocks.

Additional Comments

[codecov[bot]]

Codecov Report

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

Project coverage is 76.14%. Comparing base (0812e06) to head (24eacd5).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #1525 +/- ## =============================================== + Coverage 73.94% 76.14% +2.19% =============================================== Files 191 248 +57 Lines 11454 12918 +1464 Branches 0 370 +370 =============================================== + Hits 8470 9836 +1366 - Misses 2984 3074 +90 - Partials 0 8 +8 ```

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