Add doc comment to new render callback

packages/block-library/src/gallery/index.php

@@ -32,6 +32,17 @@ function block_core_gallery_data_id_backcompatibility( $parsed_block ) {
 
 add_filter( 'render_block_data', 'block_core_gallery_data_id_backcompatibility' );
 
+/**
+ * Adds a style tag for the --wp--style--unstable-gallery-gap var.
+ *
+ * The Gallery block needs to recalculate Image block width based on
+ * the current gap setting in order to maintain the number of flex columns
+ * so a css var is added to allow this.
+ *
+ * @param array $attributes Attributes of the block being rendered.
+ * @param string $content Content of the block being rendered.
+ * @return string The content of the block being rendered.
+ */
 function block_core_gallery_render( $attributes, $content ) {
  $gap_value = _wp_array_get( $attributes, array( 'style', 'spacing', 'blockGap' ) );
  // Skip if gap value contains unsupported characters.