docs(brrrr-lib): add example for RecordWriter

brrrr-lib/src/writer.rs

@@ -6,6 +6,24 @@ use serde::ser::Serialize;
 use std::io::Result;
 
 /// A RecordWriter writes FASTA records to the underlying source.
+///
+/// Implement this trait in order to read bioinformatic formats and write it the paricular
+/// underlying format.
+///
+/// # Examples
+///
+/// ```rust
+/// // Given our `JsonRecordWriter`, implementing the RecordWriter means it's possible to
+/// // write records in json to underlying structs that implement Write.
+/// impl<W: Write> writer::RecordWriter for JsonRecordWriter<W> {
+///     fn write_serde_record<S: Serialize>(&mut self, r: S) -> Result<()> {
+///         serde_json::to_writer(&mut self.writer, &r)?;
+///         self.writer.write_all(b"\n")?;
+///
+///         Ok(())
+///     }
+/// }
+/// ```
 pub trait RecordWriter {
     fn write_serde_record<S: Serialize>(&mut self, r: S) -> Result<()>;
 }