[scraper] move is-video function to a file

scraper/lib/video.js

@@ -0,0 +1,22 @@
+const EXTENSIONS = [
+  "3g2",
+  "3gp",
+  "avi",
+  "flv",
+  "mkv",
+  "mov",
+  "mp2",
+  "mp4",
+  "mpe",
+  "mpeg",
+  "mpg",
+  "mpv",
+  "webm",
+  "wmv",
+  "ogm"
+];
+
+module.exports = (filename) => {
+  const extensionMatch = filename.match(/\.(\w{2,4})$/);
+  return extensionMatch && EXTENSIONS.includes(extensionMatch[1].toLowerCase());
+};