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.

astra-child-hoponhopoff/assets/sprite.svg

@@ -1,4 +1,4 @@
-  <svg class="sprite" aria-hidden="true" focusable="false" xmlns="http://www.w3.org/2000/svg">
+  <svg class="sprite" aria-hidden="true" focusable="false" xmlns="http://www.w3.org/2000/svg" style="position:absolute;width:0;height:0;overflow:hidden">
     <defs>
       <path id="ringPathScroll" fill="none" d="M50,50 m-39,0 a39,39 0 1,1 78,0 a39,39 0 1,1 -78,0" />
     </defs>