Added Rust crate summary documentation comment.

rust/src/lib.rs

@@ -22,6 +22,65 @@
  */
 
 
+//! Generates QR Codes from text strings and byte arrays.
+//! 
+//! This project aims to be the best, clearest QR Code generator library.
+//! The primary goals are flexible options and absolute correctness.
+//! Secondary goals are compact implementation size and good documentation comments.
+//! 
+//! Home page with live JavaScript demo, extensive descriptions, and competitor comparisons:
+//! [https://www.nayuki.io/page/qr-code-generator-library](https://www.nayuki.io/page/qr-code-generator-library)
+//! 
+//! # Features
+//! 
+//! Core features:
+//! 
+//! - Available in 7 programming languages, all with nearly equal functionality: Java, JavaScript, TypeScript, Python, C++, C, Rust
+//! - Significantly shorter code but more documentation comments compared to competing libraries
+//! - Supports encoding all 40 versions (sizes) and all 4 error correction levels, as per the QR Code Model 2 standard
+//! - Output formats: Raw modules/pixels of the QR symbol, SVG XML string
+//! - Encodes numeric and special-alphanumeric text in less space than general text
+//! - Open source code under the permissive MIT License
+//! 
+//! Manual parameters:
+//! 
+//! - User can specify minimum and maximum version numbers allowed, then library will automatically choose smallest version in the range that fits the data
+//! - User can specify mask pattern manually, otherwise library will automatically evaluate all 8 masks and select the optimal one
+//! - User can specify absolute error correction level, or allow the library to boost it if it doesn't increase the version number
+//! - User can create a list of data segments manually and add ECI segments
+//! 
+//! # Examples
+//! 
+//! ```
+//! extern crate qrcodegen;
+//! use qrcodegen::QrCode;
+//! use qrcodegen::QrCodeEcc;
+//! use qrcodegen::QrSegment;
+//! ```
+//! 
+//! Simple operation:
+//! 
+//! ```
+//! let qr = QrCode::encode_text("Hello, world!",
+//!     QrCodeEcc::Medium).unwrap();
+//! let svg = qr.to_svg_string(4);
+//! ```
+//! 
+//! Manual operation:
+//! 
+//! ```
+//! let chrs: Vec<char> = "3141592653589793238462643383".chars().collect();
+//! let segs = QrSegment::make_segments(&chrs);
+//! let qr = QrCode::encode_segments_advanced(
+//!     &segs, QrCodeEcc::High, 5, 5, Some(2), false).unwrap();
+//! for y in 0 .. qr.size() {
+//!     for x in 0 .. qr.size() {
+//!         (... paint qr.get_module(x, y) ...)
+//!     }
+//! }
+//! ```
+
+
 /*---- QrCode functionality ----*/
 
 /// A QR Code symbol, which is a type of two-dimension barcode.