Add support for phpdoc tag @used-by

[alexkuc]

This is in reference to the built-in extension called "PHP Language Basics".

I see there is support for tag @uses but there is no support for @used-by even though both are valid phpdoc tags.

As a result, tag @used-by does not get highlighting and is not included in the preview of the function:

/**
 * @uses empty() Just a test
 * @used-by anotherFunction() Just a description
 * @return void 
 */
function sample() {
  empty(123);
}

Source code links:

• vscode/extensions/php/syntaxes/php.tmLanguage.json

  Line 2791 in ec4019f

  "match": "(?x)\n@\n(\n api|abstract|author|category|copyright|example|global|inherit[Dd]oc|internal|\n license|link|method|property(-(read|write))?|package|param|return|see|since|source|\n static|subpackage|throws|todo|var|version|uses|deprecated|final|ignore\n)\\b",

• vscode/extensions/php/syntaxes/php.tmLanguage.json

  Line 3568 in ec4019f

  "match": "(?i)\\b(spl_(classes|object_hash|autoload(_(call|unregister|extensions|functions|register))?)|class_(implements|uses|parents)|iterator_(count|to_array|apply))\\b",

[alexr00]

Moved to the repo that we get our PHP grammar from: KapitanOczywisty/language-php#19