fix: treat jfif as jpeg

issue #163

src/converters/vips.ts

@@ -1,5 +1,6 @@
 import { exec } from "node:child_process";
 
+
 // declare possible conversions
 export const properties = {
   from: {
@@ -138,4 +139,4 @@ export function convert(
       },
     );
   });
-}
+}

src/helpers/normalizeFiletype.ts

@@ -2,6 +2,7 @@ export const normalizeFiletype = (filetype: string): string => {
   const lowercaseFiletype = filetype.toLowerCase();
 
   switch (lowercaseFiletype) {
+    case "jfif":
     case "jpg":
       return "jpeg";
     case "htm":