Implement image previewing

I have tested this with png and jpeg/jpg which both work but most other image types should work as well.
![image](/attachments/25318577-d48c-4902-93b3-9adbb8b954e7)

Co-authored-by: Jan Klattenhoff <j.klattenhoff@neusta.de>
Reviewed-on: sites/file-explorer#12
Co-authored-by: jank1619 <jan@kjan.email>
Co-committed-by: jank1619 <jan@kjan.email>

src/Objects/DirContent.php

@@ -14,6 +14,7 @@ readonly class DirContent
         private string $type,
         private string $path,
         private string $content,
+        private string $mimeType,
     ) {
     }
 
@@ -24,7 +25,8 @@ readonly class DirContent
             $fileInfo->getSize() ?? 0,
             $fileInfo->getType() ?? 'N/A',
             $fileInfo->getPath(),
-            $content
+            $content,
+            mime_content_type($fileInfo->getPath() . '/' . $fileInfo->getFilename()),
         );
     }
 
@@ -57,6 +59,11 @@ readonly class DirContent
         return $this->content;
     }
 
+    public function getMimeType(): string
+    {
+        return $this->mimeType;
+    }
+
     private function getHumanReadableSize(): string
     {
         $bytes = $this->size;