Docs: Clarify the path usage register_block_type_from_metadata

The filename passed with the first param must end with `block.json`.

Fixes #53806.
Props coreyw, costdev.



git-svn-id: https://develop.svn.wordpress.org/trunk@52012 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/blocks.php

@@ -213,6 +213,7 @@ function get_block_metadata_i18n_schema() {
  *
  * @param string $file_or_folder Path to the JSON file with metadata definition for
  *                               the block or path to the folder where the `block.json` file is located.
+ *                               If providing the path to a JSON file, the filename must end with `block.json`.
  * @param array  $args           Optional. Array of block type arguments. Accepts any public property
  *                               of `WP_Block_Type`. See WP_Block_Type::__construct() for information
  *                               on accepted arguments. Default empty array.