Add file existence check in FileGetContents class

A check for file existence has been added to the FileGetContents class. Now, before file content is retrieved, the system will check whether the file exists. This reduces the likelihood of encountering a SqlFileNotReadableException.

src/FileGetContents.php

@@ -6,6 +6,7 @@
 
 use Ray\Query\Exception\SqlFileNotReadableException;
 
+use function file_exists;
 use function file_get_contents;
 
 final class FileGetContents implements FileGetContentsInterface
@@ -15,6 +16,10 @@ final class FileGetContents implements FileGetContentsInterface
      */
     public function __invoke(string $filePath): string
     {
+        if (! file_exists($filePath)) {
+            throw new SqlFileNotReadableException($filePath);
+        }
+
         $content =  file_get_contents($filePath);
         if ($content === false) {
             // @codeCoverageIgnoreStart