How can I customize the "H5P - Create and Share Rich Content and Applications" module?

All the hooks listed in the h5p.api.php file for the Drupal 7 version are still supported from the Drupal 8 version. The Drupal 8 branch doesn't have a h5p.api.php file to document the used hooks, but the code invokes the same hooks. See the following list, which reports where each hook is invoked.

• hook_h5p_semantics_alter(): src/H5PDrupal/H5PDrupal.php

  $version = $majorVersion . '.'. $minorVersion;
  \Drupal::moduleHandler()->alter('h5p_semantics', $semantics, $name, $version);
  

• hook_h5p_filtered_params_alter(): src/H5PDrupal/H5PDrupal.php

  $moduleHandler = \Drupal::moduleHandler();
  $filteredAsJson = json_decode($filteredParameters);
  $moduleHandler->alter('h5p_filtered_params', $filteredAsJson);
  

• hook_h5p_styles_alter() and hook_h5p_scripts_alter(): src/Controller/H5PEmbed.php

  $mode = 'external';
  \Drupal::moduleHandler()->alter('h5p_scripts', $files['scripts'], $library_list, $mode);
  \Drupal::moduleHandler()->alter('h5p_styles', $files['styles'], $library_list, $mode);
  

• hook_h5p_library_installed(): src/H5PDrupal/H5PDrupal.php

  \Drupal::moduleHandler()->invokeAll('h5p_library_installed', array($libraryData, $new));