Modify regex and add more tests based on PR review feedback

Author: rodrigoprimo

src/Standards/Squiz/Sniffs/Commenting/PostStatementCommentSniff.php

@@ -110,7 +110,7 @@ public function process(File $phpcsFile, $stackPtr)
         }
 
         if ($phpcsFile->tokenizerType === 'PHP'
-            && preg_match('|//\s?@[^\s]+|', $tokens[$stackPtr]['content']) === 1
+            && preg_match('|^//[ \t]*@[^\s]+|', $tokens[$stackPtr]['content']) === 1
         ) {
             $error = 'Annotations may not appear after statements';
             $phpcsFile->addError($error, $stackPtr, 'AnnotationFound');

src/Standards/Squiz/Tests/Commenting/PostStatementCommentUnitTest.inc

@@ -53,6 +53,12 @@ $match = match($foo // comment
     1 => 1, // comment
 };
 
-$a = 1; // @codeCoverageIgnore
-$b = 2; //@phpstan-ignore variable.undefined
-$c = 3; //  @thisIsNotAnAnnotation - more than one space before the @ symbol.
+// Comments recognized as annotations by PHPCS.
+$a = 1; //@codeCoverageIgnore
+$b = 2; // @phpstan-ignore variable.undefined
+$c = 3; //  @phpstan-ignore variable.undefined
+$d = 4; //	@tabInsteadOfSpace
+
+// Comments that include `@`, but are not recognized as annotations by PHPCS.
+$a = 1; // @ = add tag.
+$b = 2; // Some comment. // @username

src/Standards/Squiz/Tests/Commenting/PostStatementCommentUnitTest.inc.fixed

@@ -58,7 +58,14 @@ $match = match($foo // comment
 // comment
 };
 
-$a = 1; // @codeCoverageIgnore
-$b = 2; //@phpstan-ignore variable.undefined
-$c = 3; 
-//  @thisIsNotAnAnnotation - more than one space before the @ symbol.
+// Comments recognized as annotations by PHPCS.
+$a = 1; //@codeCoverageIgnore
+$b = 2; // @phpstan-ignore variable.undefined
+$c = 3; //  @phpstan-ignore variable.undefined
+$d = 4; //	@tabInsteadOfSpace
+
+// Comments that include `@`, but are not recognized as annotations by PHPCS.
+$a = 1; 
+// @ = add tag.
+$b = 2; 
+// Some comment. // @username

src/Standards/Squiz/Tests/Commenting/PostStatementCommentUnitTest.php

@@ -40,9 +40,12 @@ public function getErrorList($testFile='')
                 18 => 1,
                 35 => 1,
                 53 => 1,
-                56 => 1,
                 57 => 1,
                 58 => 1,
+                59 => 1,
+                60 => 1,
+                63 => 1,
+                64 => 1,
             ];
 
         case 'PostStatementCommentUnitTest.1.js':