fix fatal mistake in the b64 detector

src/core/base64/extractBase64.mts

@@ -15,9 +15,7 @@ export function extractBase64(base64: string = ""): {
 } {
   // console.log(`extractBase64(${base64.slice(0, 120)})`)
   // Regular expression to extract the MIME type and the base64 data
-  const matches = base64.match(/^data:([A-Za-z-+/]+);base64,(.+)$/)
-
-  // console.log("matches:", matches)
+  const matches = base64.match(/^data:([A-Za-z-+0-9/]+);base64,(.+)$/)
 
   if (!matches || matches.length !== 3) {
     throw new Error("Invalid base64 string")