Add two chapters as TODO and change intro

Author: skade

docs/src/SUMMARY.md

@@ -1,7 +1,7 @@
 # Summary
 
-- [Welcome to `async-std`!](./overview.md)
-  - [`async-std`](./overview/async-std.md)
+- [Introduction](./introduction.md)
+  - [Welcome to `async-std`!](./overview/async-std.md)
   - [`std::future` and `futures-rs`](./overview/std-and-library-futures.md)
   - [Stability guarantees](./overview/stability-guarantees.md)
 - [Async concepts using async-std](./concepts.md)

docs/src/concepts/async-read-write.md

@@ -1 +1 @@
-# Async read/write
+# TODO: Async read/write

docs/src/concepts/streams.md

@@ -1 +1 @@
-# Streams
+# TODO: Streams

docs/src/introduction.md

@@ -0,0 +1,7 @@
+# Introduction
+
+This book serves as high-level documentation for `async-std` and a way of learning async programming in Rust through it. As such, i focusses on the `async-std` and its task model give you.
+
+Please note that the Rust project provides its own book on asynchronous programming, called ["Asynchronous Programming in Rust"][async-book], which we highly recommend reading along with this book, as it provides a different, wider view on the topic.
+
+[async-book]: https://rust-lang.github.io/async-book/

docs/src/overview.md

@@ -1 +1,10 @@
-# async-std
+# Welcome to `async-std`
+
+![async-std logo](./images/horizontal_color.svg)
+
+`async-std` along with its [supporting libraries][organization] is a library making your life in async programming easier. It provides provide fundamental implementations for downstream libraries and applications alike. The name reflects the approach of this library: it is a closely modeled to the Rust main standard library as possible, replacing all components by async counterparts.
+
+`async-std` provides an interface to all important primitives: filesystem operations, network operations and concurrency basics like timers. It also exposes an `task` in a model similar to the `thread` module found in the Rust standard lib.  But it does not only include io primitives, but also `async/await` compatible versions of primitives like `Mutex`. You can read more about `async-std` in [the overview chapter][overview-std].
+
+[organization]: https://github.com/async-rs/async-std
+[overview-std]: overview/async-std/