message: Render additionalPropsTables with <h3>
diff: @@ -307,11 +307,16 @@ function propsTable(
  exports: Node[],
  dir: string,
  titleAndDocs = true,
  + headingLevel = 2,
  ) {
  let markdown = '';
  if (titleAndDocs) {
  - markdown += `<a name="${name}"></a>\n\n## ${name}\n\n`;
  + let heading = '';
  + for (let hh = 0; hh < headingLevel; hh++) {
  + heading += '#';
  + }
  + markdown += `<a name="${name}"></a>\n\n${heading} ${name}\n\n`;
  markdown += `${docs ? `${strip(docs.content).trim()}\n\n` : ''}`;
  }
  @@ -414,7 +419,15 @@ function propType(value: any, exports: any[], dir: string): any {
  return propType(local.value, exports, dir);
  case 'InterfaceType':
  additionalPropsTables.push(
  - propsTable(value.name, value.docs, value.properties, exports, dir),
  + propsTable(
  + value.name,
  + value.docs,
  + value.properties,
  + exports,
  + dir,
  + true,
  + 3,
  + ),
  );
  return `<code><a href="#${value.name}">${value.name}</a>${params}</code>`;
  case 'UnionType':
  