feat: radar style tweak ups

[antongolub]

Hey guys,

Thanks for your project. This is an awesome and clear tech stack visualization. We've slightly modified it for our bloody enterprise purposes, and I'd like to suggest a pinch of our tweak ups:

1. Radar date on a new line
2. Bold accented groups headers
3. Colored ring labels

Before:

After:

[r3code]

Why not merged?

[bocytko]

Thanks for the adjustments and your patience with this PR @antongolub 🙏

In a follow-up PR (#102), I've adjusted the color palette for improved contrast.