message: Fixing snippet example
diff: @@ -24,7 +24,8 @@ fn main() -> tantivy::Result<()> {
  // # Defining the schema
  let mut schema_builder = SchemaBuilder::default();
  - schema_builder.add_text_field("body", TEXT);
  + let title = schema_builder.add_text_field("title", TEXT | STORED);
  + let body = schema_builder.add_text_field("body", TEXT | STORED);
  let schema = schema_builder.build();
  // # Indexing documents
  @@ -32,9 +33,6 @@ fn main() -> tantivy::Result<()> {
  let mut index_writer = index.writer(50_000_000)?;
  - let title = schema.get_field("title").unwrap();
  - let body = schema.get_field("body").unwrap();
  -
  // we'll only need one doc for this example.
  index_writer.add_document(doc!(
  title => "Of Mice and Men",
  