code: @NonNull
      @SuppressWarnings("unused")
      public ReportBuilder customData(@NonNull String key, String value) {
          customData.put(key, value);
          return this;
      }
docs: Sets an additional value to be added to {@link org.acra.ReportField#CUSTOM_DATA}. The value
  specified here takes precedence over globally specified custom data.
  
  @param key   the key identifying the custom data
  @param value the value for the custom data entry
  @return the updated {@code ReportBuilder}