add standard markdown badges to the readme (#131)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a4c6f0e..6e0aa77 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,5 @@
+## 3.0.3-dev
+
 ## 3.0.2
 
 * Require Dart 2.14.0.
diff --git a/README.md b/README.md
index c4f98a1..0ab07be 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,8 @@
-# Cryptographic hashing functions for Dart
+[![Dart CI](https://github.com/dart-lang/crypto/actions/workflows/test-package.yml/badge.svg)](https://github.com/dart-lang/crypto/actions/workflows/test-package.yml)
+[![pub package](https://img.shields.io/pub/v/crypto.svg)](https://pub.dev/packages/crypto)
+[![package publisher](https://img.shields.io/pub/publisher/crypto.svg)](https://pub.dev/packages/crypto/publisher)
 
-A set of cryptographic hashing functions implemented in pure Dart
+A set of cryptographic hashing functions for Dart.
 
 The following hashing algorithms are supported:
 
@@ -49,6 +51,7 @@
 
 ```dart
 import 'dart:convert';
+
 import 'package:convert/convert.dart';
 import 'package:crypto/crypto.dart';
 
diff --git a/pubspec.yaml b/pubspec.yaml
index 18656ce..83831f4 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: crypto
-version: 3.0.2
-description: Implementations of SHA, MD5, and HMAC cryptographic functions
+version: 3.0.3-dev
+description: Implementations of SHA, MD5, and HMAC cryptographic functions.
 repository: https://github.com/dart-lang/crypto
 
 environment: