[EuiIcon] Add sun glyph

[elizabetdev]

Summary

This PR adds a sun glyph to EuiIcon.

The idea of the sun is to be used to toggle dark and light modes, so I focused on making the icon look similar to the moon icon. That's the reason the icon is filled and not linear.

The ray of the sun could have 1px to fit the grid. But this would make the icon not being centered and look smaller when compared with the moon. So I ended up with rays of 1.5px.

In case there's an animation to toggle from a moon to sun the animation would look better. Both icons will have the same center and similar weight.

Here are some tests: https://codesandbox.io/s/eager-field-i8r8q?file=/demo.js

Design

Dark and light themes

My computer is using the macOS Monterey. I no longer have the option to open the browser in low res. So I'm using the following app http://easyresapp.com/ to test in low res. Hopefully, the tests correspond to reality.

Checklist

• Check against all themes for compatibility in both light and dark modes
• Checked in mobile
• Checked in Chrome, Safari, Edge, and Firefox
• Props have proper autodocs and playground toggles
• Added documentation
• Checked Code Sandbox works for any docs examples
• Added or updated jest and cypress tests
• Checked for breaking changes and labeled appropriately
• Checked for accessibility including keyboard-only and screenreader modes
• A changelog entry exists and is marked appropriately

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5548/

[cchaos]

😻 Love it. I think the 1.5 stroke was the right choice. Lines don't always have to be crisp unless the blurriness loses the shape. But here it actually helps. Here's a screenshot from my firefox, seems similar to yours:

And thanks for the codesandbox! Pretty cool to see it in action.

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5548/