Documentation, Metadata & Media improvements

[Seramis]

Description

• Updated README.md and all packages' PACKAGE.md with better formatting and wording.
• Restored MessagePack integration section that got lost with earlier changes.
• Updated all images to newer branding style.
• Updated all NuGet projects to use their own logo images.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Other (please specify): Branding/Image media

Checklist

• The PR is submitted to the correct branch (main).
• My code follows the project's coding style. (.editorconfig)
• I have commented my code, particularly in hard-to-understand areas and public interfaces.
• I have added or updated tests for the changes I made.
• All new and existing tests passed.
• I have updated the documentation where applicable.

Testing Instructions

Create a pre-release and check for all documentation and imagery in nuget.org.