Fix checking to filename ADR valid

Author: globtec

src/Filesystem/Workspace.php

@@ -145,7 +145,7 @@ private function isValidFilename(SplFileInfo $fileinfo) : bool
             return false;
         }
 
-        $pattern = '/^\d{' . DecisionRecord::NUMBER_LENGTH . '}-[a-z\-]+\\' . DecisionRecord::EXTENSION . '$/';
+        $pattern = '/^\d{' . DecisionRecord::NUMBER_LENGTH . '}-[a-z\d\-]+\\' . DecisionRecord::EXTENSION . '$/';
 
         return (boolean) preg_match($pattern, $fileinfo->getFilename());
     }

tests/Filesystem/WorkspaceTest.php

@@ -36,10 +36,15 @@ public function testCount()
 
         $vfs->addChild(vfsStream::newFile('0001-foo.md'));
         $vfs->addChild(vfsStream::newFile('0002-bar.md'));
+        $vfs->addChild(vfsStream::newFile('0003-baz-2.md'));
+        
+        $vfs->addChild(vfsStream::newFile('0004-snake_case.md'));
+        $vfs->addChild(vfsStream::newFile('0005-UPPERCASE.md'));
+        $vfs->addChild(vfsStream::newFile('0006-CamelCase.md'));
         $vfs->addChild(vfsStream::newFile('any-file.md'));
         $vfs->addChild(vfsStream::newDirectory('any-directory'));
 
-        $this->assertEquals(2, $workspace->count());
+        $this->assertEquals(3, $workspace->count());
     }
 
     public function testAdd()