Update logo files

[brklyn8900]

Resolves #108

Brief description

Add Koinos logo with purple icon. Add square icons to the media page.

Checklist

• [x] I have built this pull request locally
• [ ] I have ran the unit tests locally
• [x] I have manually tested this pull request
• [x] I have reviewed my pull request
• [ ] I have added any relevant tests

Demonstration

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