format(output): reformat markdown renderer according google format

Author: quen2404

src/main/java/com/qdesrame/openapi/diff/compare/SchemaDiff.java

@@ -84,7 +84,7 @@ protected static Schema resolveComposedSchema(Components components, Schema sche
     return schema;
   }
 
-  protected static Schema addSchema(Schema schema, Schema fromSchema) {
+  protected static Schema addSchema(Schema<?> schema, Schema<?> fromSchema) {
     if (fromSchema.getProperties() != null) {
       if (schema.getProperties() == null) {
         schema.setProperties(fromSchema.getProperties());

src/main/java/com/qdesrame/openapi/diff/output/MarkdownRender.java

@@ -175,8 +175,8 @@ protected String itemResponse(String title, String code, String description) {
   protected String headers(ChangedHeaders headers) {
     StringBuilder sb = new StringBuilder();
     if (headers != null) {
-      sb.append(listHeader("New header", headers.getIncreased()));
-      sb.append(listHeader("Deleted header", headers.getMissing()));
+      sb.append(listHeader("New header", headers.getIncreased()))
+          .append(listHeader("Deleted header", headers.getMissing()));
       headers
           .getChanged()
           .entrySet()