Icon edit code in sandbox

[AlitaBernachot]

📦 Add an icon to open and edit the example in code sandbox

Updated example pages (Work In Progress):

• exports.html
• icon-position.html
• layer-group.html => ❌ icon OK but example KO (even not in code sandbox)
• mvt.html
• overlay.html => ❌ icon OK but black bg for 3d map KO
• rotate.html
• synthvectors.html
• wmts.html
• customProj.html
• groundvectors.html
• imageWMS.html
• kml.html => ❌ simple example KO
• main.html
• rastersync.html
• sidebyside.html
• vectors.html
• buildings.html
• fillstyle.html
• image-static.html
• lazy.html => ❌ button for code sandbox OK but example KO in sandbox
• oldfashioned.html
• print.html
• selection.html
• tracking.html

⚡️ To improve:

• add a way to add special files according to the example (for now, all files are included for all examples)
• enable the inclusion of a css or a script in the html tag (instead of adding the tag in the html body