docs: improve the README, add symlinks to sub-crates

Author: aqrln

README.md

@@ -4,17 +4,76 @@
 
 High-level N-API bindings for Node.js addons written in Rust.
 
-This project is covered by a [Code of Conduct](CODE_OF_CONDUCT.md).
+**Warning**: this is a proof-of-concept implementation that's not intended
+for use yet. The project is under initial phase of development, the API is a
+quite sketchy and is going to be refactored heavily. If you are interested in
+contributing, though, it is super welcome!
+
+The project is covered by a [Code of Conduct][coc].
 
 ## Crates
 
-* `napi-sys`: low-level bindings to N-API generated from
+* [`napi-sys`][napi-sys]: low-level bindings to N-API generated from
   [`node_api.h`](https://github.com/nodejs/node/blob/master/src/node_api.h)
   using [`bindgen`](https://github.com/rust-lang-nursery/rust-bindgen).
-* `napi`: high-level and rusty wrappers around `napi-sys`.
-* `napi-derive`: contains a procedural macro that allows to construct typesafe
-   structures that represent function parameters from JavaScript function call
-   arguments and automatically validate them.
+* [`napi`][napi]: high-level and rusty wrappers around `napi-sys`.
+* [`napi-derive`][napi-derive]: contains a procedural macro that allows to
+  construct typesafe structures that represent N-API callback parameters and
+  automatically validate the arguments that JavaScript code passes in.
+
+## Example
+
+Check out <https://github.com/aqrln/napi-rs/tree/master/example> to see the
+full source code and project structure of this example.
+
+### `lib.rs`
+
+```rust
+#[macro_use]
+extern crate napi;
+#[macro_use]
+extern crate napi_derive;
+
+use napi::{NapiEnv, NapiNumber, NapiResult, NapiUndefined};
+
+#[derive(NapiArgs)]
+struct HelloArgs;
+
+fn hello<'a>(env: &'a NapiEnv, _: &HelloArgs) -> NapiResult<NapiUndefined<'a>> {
+    println!("Hello from the Rust land!");
+    NapiUndefined::new(env)
+}
+
+#[derive(NapiArgs)]
+struct AddArgs<'a> {
+    first: NapiNumber<'a>,
+    second: NapiNumber<'a>,
+}
+
+fn add<'a>(env: &'a NapiEnv, args: &AddArgs<'a>) -> NapiResult<NapiNumber<'a>> {
+    let first = args.first.to_i32()?;
+    let second = args.second.to_i32()?;
+    NapiNumber::from_i32(env, first + second)
+}
+
+napi_callback!(example_hello, hello);
+napi_callback!(example_add, add);
+```
+
+### `example.js`
+
+```javascript
+'use strict';
+
+const addon = require('./build/Release/example.node');
+
+addon.hello();
+console.log(addon.add(1, 2));
+```
 
+[coc]: https://github.com/aqrln/napi-rs/blob/master/CODE_OF_CONDUCT.md
+[napi]: https://crates.io/crates/napi
+[napi-derive]: https://crates.io/crates/napi-derive
+[napi-sys]: https://crates.io/crates/napi-sys
 [travis-badge]: https://travis-ci.org/aqrln/napi-rs.svg?branch=master
 [travis-url]: https://travis-ci.org/aqrln/napi-rs

napi-derive/LICENSE

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+../LICENSE

napi-derive/README.md

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+../README.md

napi-sys/LICENSE

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+../LICENSE

napi-sys/README.md

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+../README.md

napi/LICENSE

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+../LICENSE

napi/README.md

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+../README.md