Update Markdown to recommended best practices

[chartgerink]

This PR adjusts some of the markdown practices according to the recommended best practices.

Specifically:

• Adjust the heading levels to have one Header1 (title; # Header1) and rest be at least Heading2.
• Format italic as *italic* instead of _italic
• Format bold as **bold** instead of __bold__

I saw this while reading through the report - I fully understand this is pedantic and I have zero expectation for this to be merged if this is unhelpful. I figured I'd make this PR for the off case it would be helpful 😊

[codecov-commenter]

Codecov Report

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

Comparison is base (fb004c9) 70.83% compared to head (68656ae) 73.07%. Report is 8 commits behind head on main.

:exclamation: Current head 68656ae differs from pull request most recent head 67568ac. Consider uploading reports for the commit 67568ac to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #126 +/- ## ========================================== + Coverage 70.83% 73.07% +2.24% ========================================== Files 4 4 Lines 24 26 +2 ========================================== + Hits 17 19 +2 Misses 7 7 ```

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