feat: color swatches for layers and layer groups

[spectrachrome]

Implemented changes

To make it easier to associate layers with additional information in a parent app, this pull requests implements color swatches for individual layers. These automatically replace the icons of layers and layer groups with the color swatch as long as the color attribute is set in the OpenLayers layer.

Screenshots/Videos

Checklist before requesting a review

• I have performed a self-review of my code
• I have added a test related to this feature/fix
• For new features: I have created a story showcasing this new feature
• All checks have passed
• The PR title follows conventional commit style and reflects the type of change (major/minor/patch, breaking)
• The PR title describes the change within this element (each merged PR equals one entry in the element's changelog!)

[netlify]

✅ Deploy Preview for eoxelements ready!

Name	Link
🔨 Latest commit	08d532d
🔍 Latest deploy log	https://app.netlify.com/sites/eoxelements/deploys/674737c5486094000732b91f
😎 Deploy Preview	https://deploy-preview-1379--eoxelements.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[silvester-pari]

Thank you!