chore(readme): update with usage and options

Author: mateonunez

README.md

@@ -14,24 +14,38 @@ npm install fastify-at-mysql
 
 ## Getting Started
 
+The `fastify-at-mysql` plugin is a wrapper around the `@databases/mysql` package. It exposes the `mysql` property on the Fastify instance.
+
 ```js
 const Fastify = require('fastify')
 const fatsifyMysql = require('fastify-at-mysql')
 
 const fastify = fastify()
 fastify.register(fatsifyMysql, {
-  host: '',
-  user: '',
-  password: '',
-  database: '',
+  host: process.env.DB_HOST,
+  user: process.env.DB_USER,
+  password: process.env.DB_PASS,
+  database: process.env.DB_NAME,
 })
 
 fastify.get('/', async (request, reply) => {
-  const result = await fastify.mysql.query('SELECT 1 + 1 AS solution')
+  const result = await fastify.mysql.query('SELECT * FROM contributors')  
   reply.send(result)
 })
 ```
 
+The `query` method returns a `Promise` that resolves to an array of objects. Each object represents a row in the result set. It wraps the `sql` method from `@databases/mysql` package that prevents SQL injection attacks.
+
+## Options
+
+The plugin accepts the following options:
+
+- `host` - The hostname of the database you are connecting to. (Default: `localhost`)
+- `port` - The port number to connect to. (Default: `3306`)
+- `user` - The MySQL user to authenticate as.
+- `password` - The password of that MySQL user.
+- `database` - Name of the database to use for this connection (Optional).
+
 ## License
 
-FastifyAtMysql is licensed under the [MIT](LICENSE) license.
+**fastify-at-mysql** is licensed under the [MIT](LICENSE) license.