Improve the documentation

Author: mnapoli

README.md

@@ -3,13 +3,13 @@ All you need to log with [Bref](https://bref.sh) on AWS Lambda.
 [![Build Status](https://img.shields.io/travis/brefphp/logger/master.svg?style=flat-square)](https://travis-ci.org/brefphp/logger)
 [![Latest Version](https://img.shields.io/github/release/bref/logger.svg?style=flat-square)](https://packagist.org/packages/bref/logger)
 
-Bref/Logger is a lightweight [PSR-3](https://www.php-fig.org/psr/psr-3/) logger for AWS Lambda. Messages are sent to stderr so that they end up in [CloudWatch](https://bref.sh/docs/environment/logs.html).
+Bref/Logger is a lightweight [PSR-3](https://www.php-fig.org/psr/psr-3/) logger for AWS Lambda. Messages are sent to `stderr` so that they end up in [CloudWatch](https://bref.sh/docs/environment/logs.html).
 
 ## Why?
 
-As explained in [the Bref documentation](https://bref.sh/docs/environment/logs.html), logging in AWS Lambda means logging to stderr. Logs written to stderr are automatically sent to CloudWatch, AWS' solution to collect and view logs.
+As explained in [the Bref documentation](https://bref.sh/docs/environment/logs.html), logging in AWS Lambda means logging to `stderr`. Logs written to `stderr` are automatically sent to [CloudWatch](https://aws.amazon.com/cloudwatch/), AWS' solution to collect and view logs.
 
-While classic loggers like [Monolog](https://github.com/Seldaek/monolog) work fine, this logger comes as a simpler and lighter alternative. It does not require any configuration and currently contains a single class.
+While classic loggers like [Monolog](https://github.com/Seldaek/monolog) work fine, this logger comes as a simpler and lighter alternative optimized for AWS Lambda. It does not require any configuration and currently contains a single class.
 
 Since it is [PSR-3](https://www.php-fig.org/psr/psr-3/) compliant, Bref/Logger is also compatible with any framework or library consuming a PSR-3 logger.
 
@@ -43,7 +43,9 @@ $logger->error('This is an error');
 [ERROR] This is an error
 ```
 
-[PSR-3 placeholders](https://www.php-fig.org/psr/psr-3/#12-message) can be used to insert information into a message without having to concatenate strings manually:
+### Message placeholders
+
+[PSR-3 placeholders](https://www.php-fig.org/psr/psr-3/#12-message) can be used to insert information from the `$context` array into the message without having to concatenate strings manually:
 
 ```php
 $logger->warning('Invalid login attempt for email {email}', [
@@ -56,6 +58,8 @@ $logger->warning('Invalid login attempt for email {email}', [
 [WARNING] Invalid login attempt for email johndoe@example.com
 ```
 
+### Logging exceptions
+
 Exceptions [can be logged](https://www.php-fig.org/psr/psr-3/#13-context) under the `exception` key:
 
 ```php