Add small patterns library

docs/src/SUMMARY.md

@@ -17,6 +17,7 @@
   - [Proper Shutdown](./patterns/proper-shutdown.md)
   - [Background Tasks](./patterns/background-tasks.md)
   - [Testing](./patterns/testing.md)
+  - [Collected Small Patterns](./patters/small-patterns.md)
 - [Security practices](./security/index.md)
   - [Security disclosures and policy](./security/policy.md)
 - [Glossary](./glossary.md)

docs/src/patterns.md

@@ -1 +1,5 @@
-# Async Patterns
+# Patterns
+
+This section documents small, useful patterns.
+
+It is intended to be read at a glance, allowing you to get back when you have a problem.

docs/src/patterns/small-patterns.md

@@ -0,0 +1,18 @@
+# Small Patterns
+
+A collection of small, useful patterns.
+
+<!-- toc -->
+
+## Splitting streams
+
+`async-std` doesn't provide a `split()` method on `io` handles. Instead, splitting a stream into a read and write half can be done like this:
+
+```rust
+use async_std::io;
+
+async fn echo(stream: io::TcpStream) {
+    let (reader, writer) = &mut (&stream, &stream);
+    io::copy(reader, writer).await?;
+}
+```