feat: Add new m365 icon, add brand icons page to docs, and refactor code

[sopranopillow]

This PR adds the following:

• Adds test, start, and build commands.
• Adds a new section to the docs to visualize the brand icons.
• Refactors cdn url usage and updates to latest cdn link.
• Adds new m365 icons.

Fixes https://github.com/microsoft/fluentui/issues/25928