Fix #1879 Include fullscreen button in embed pages

[allyoucanmap]

This PR improves the share embed section to include the fullscreen plugin, the embed share link has been converted from url to iframe snippet.

Now when an embed page uses the allowFullscreen=true query param the fullscreen button will be added in a menu to the bottom of the iframe.

In the screenshot on the left embed whithout fullscreen and on the right with fullscreen

New embed section in share panel

[github-actions]

The backport to 4.4.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-4.4.x 4.4.x
# Navigate to the new working tree
cd .worktrees/backport-4.4.x
# Create a new branch
git switch --create backport-1880-to-4.4.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 5821ad2a49cdfaa73054d53251d3f9f1027e1129
# Push it to GitHub
git push --set-upstream origin backport-1880-to-4.4.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-4.4.x

Then, create a pull request where the base branch is 4.4.x and the compare/head branch is backport-1880-to-4.4.x.