Clean up installation instructions in README.md

[austin-denoble]

Problem

The installation instructions in the README.md could be a bit clearer. We also need an example for calling uninstall via script.

Solution

Reorder installation instructions in the README, add a callout for the uninstall.sh script.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

n/a