Permit to customize LINK regex

[RobinDev]

This proposal permit to customize link regex

(i would like to be able to grab them into inline comment so i need to change the regex to ^(\.{1,2}[/\\])?([^:# ]+)?(:\d+|#[\w-]+)?, eg :

<!-- LINK example.html -->
<?php // LINK example.php ?>
<?php /* LINK example.php */ ?>

[macjuul]

Looks like a good change to me. Would you be so kind to additionally declare this new setting in the package.json as well as the README.md?

From a code style perspective it would be preferred to leave the default regex as a constant as it was originally, however renamed to DEFAULT_LINK_REGEX.

Nevertheless, thanks for the PR!