feat: Enhance gallery functionality with lightbox feature and improve icon sprite accessibility

- Added a lightbox feature for gallery images, allowing users to view photos in a modal with navigation controls.
- Updated the SVG sprite to include inline styles for better accessibility.
- Increased CSS specificity by doubling the `.vc-app` class to ensure styles override Astra theme defaults.
- Introduced new shortcodes for bus tours, about section, and articles in the VC_Sections class.
- Improved the handling of featured images in the single tour template for sharper display.
- Updated version number to 1.8.15.

viator-collector/includes/helpers.php

@@ -595,7 +595,10 @@ function vc_print_icon_sprite() {
  * e.g. vc_icon( 'star', 'rating__star' ) => <svg class="icon rating__star">…</svg>
  */
 function vc_icon( $name, $extra_class = '' ) {
-	$name  = preg_replace( '/[^a-z0-9\-]/', '', 'i-' . ltrim( (string) $name, 'i-' ) );
+	// Strip an existing "i-" prefix (once), then re-add it. ltrim() with a
+	// charlist would eat any leading i/-, turning "instagram" into "nstagram".
+	$slug  = preg_replace( '/^i-/', '', (string) $name );
+	$name  = preg_replace( '/[^a-z0-9\-]/', '', 'i-' . $slug );
 	$class = 'icon' . ( $extra_class ? ' ' . $extra_class : '' );
 	return '<svg class="' . esc_attr( $class ) . '" aria-hidden="true"><use href="#' . esc_attr( $name ) . '"></use></svg>';
 }