chore: add margin to bottom of logo to avoid overcrowding in readme

[JamesLMilner]

Description of Changes

Adds a small margin under the new logo to avoid visual clutter

Link to Issue

No issue

PR Checklist

• [x] The PR title follows the conventional commit standard
• [ ] There is a associated GitHub issue
• [ ] If I have added significant code changes, there are relevant tests
• [ ] If there are behaviour changes these are documented