Minor formatting changes in the README file
Add Composer dependency declaration example to the README file
Replace @link with @see PHPDoc tag

As per proposed PSR-5, usage of @see PHPDoc tag is recommended instead
of @link PHPDoc tag.
Remove @package PHPDoc tag

Since class namespaces match logical subdivision, @package PHPDoc tag is
redundant. Removal will also prevent unnecessary maintenance overhead.
Use SPDX identifier in the @license PHPDoc tag

As per PSR-5 recommendation.