cbor: prepare for publishing as standalone crate

- Add an example of usage
- Add a minimal README, including the example code
- Document public items
- Add more info to Cargo.toml

libraries/cbor/README.md

@@ -0,0 +1,63 @@
+# CBOR Parsing Library
+
+This crate implements Concise Binary Object Representation (CBOR) from [RFC
+8949](https://datatracker.ietf.org/doc/html/rfc8949).
+
+## Usage
+
+```rust
+fn main() {
+    // Build a CBOR object with various different types included. Note that this
+    // object is not built in canonical order.
+    let manual_object = Value::Map(vec![
+        (
+            Value::Unsigned(1),
+            Value::Array(vec![Value::Unsigned(2), Value::Unsigned(3)]),
+        ),
+        (
+            Value::TextString("tstr".to_owned()),
+            Value::ByteString(vec![1, 2, 3]),
+        ),
+        (Value::Negative(-2), Value::Simple(SimpleValue::NullValue)),
+        (Value::Unsigned(3), Value::Simple(SimpleValue::TrueValue)),
+    ]);
+
+    // Build the same object using the crate's convenience macros.
+    let macro_object = cbor_map! {
+        1 => cbor_array![2, 3],
+        "tstr" => cbor_bytes!(vec![1, 2, 3]),
+        -2 => cbor_null!(),
+        3 => cbor_true!(),
+    };
+
+    assert_eq!(manual_object, macro_object);
+    println!("Object {:?}", manual_object);
+
+    // Serialize to bytes.
+    let mut manual_data = vec![];
+    sk_cbor::writer::write(manual_object, &mut manual_data);
+    let hex_manual_data = hexify(&manual_data);
+
+    // Serialized version is in canonical order.
+    println!("Serializes to {}", hex_manual_data);
+    assert_eq!(
+        hex_manual_data,
+        concat!(
+            "a4",         // 4-map
+            "01",         // int(1) =>
+            "820203",     // 2-array [2, 3],
+            "03",         // int(3) =>
+            "f5",         // true,
+            "21",         // nint(-2) =>
+            "f6",         // null,
+            "6474737472", // 4-tstr "tstr" =>
+            "43010203"    // 3-bstr
+        )
+    );
+
+    // Convert back to an object.  This is different than the original object,
+    // because the map is now in canonical order.
+    let recovered_object = sk_cbor::reader::read(&manual_data).unwrap();
+    println!("Deserializes to {:?}", recovered_object);
+}
+```