fix getFileExtension missing numeric extensions (e.g. mp4)

Jacky Zhao

2023-08-09 e4950e06a15e34134b9feb064749748080bd59a1

 quartz/path.test.ts

@@ -145,6 +145,7 @@
        ["/content/index.md", "content/index"],
        ["content/cool.png", "content/cool"],
        ["index.md", "index"],
        ["test.mp4", "test"],
        ["note with spaces.md", "note-with-spaces"],
      ],
      path.slugifyFilePath,