Add exclude regexp to exclude certain URL's from being automatically converted to linky enities.

This was a pretty small change with a new config entry.

1. +++ b/config/install/linkyreplacer.settings.yml
   @@ -2,3 +2,4 @@ internal_patterns: ""
   +exclude_patter: ''
   

   We need a post update hook to update the existing config.

2. +++ b/src/LinkyEntityUtility.php
   @@ -167,6 +167,14 @@ class LinkyEntityUtility implements LinkyEntityUtilityInterface {
   +    if ($exclude = $this->configFactory->get('linkyreplacer.settings')->get('exclude_pattern')) {
   

   We need some kind of validation for valid regex.

3. +++ b/src/LinkyEntityUtility.php
   @@ -167,6 +167,14 @@ class LinkyEntityUtility implements LinkyEntityUtilityInterface {
   +      if (preg_match($exclude, $href)) {
   

   We need tests for this.

1. I have fixed up the typo and added in an update to update to set the default value.
2. I have looked into this and to test the regular expression is to use preg_match(). If the expression is invalid it will return false, as opposed to not matching which will return 0.
3. I have added in a test to check the if the exclusion will work.