chore: add fileToBase64

Author: Simon he

src/fileToBase64.ts

@@ -0,0 +1,9 @@
+export function fileToBase64(file: File) {
+  return new Promise((resolve, reject) => {
+    let reader = new FileReader();
+    reader.readAsDataURL(file)
+    reader.onload = function (e) {
+      resolve(e?.target?.result)
+    }
+  })
+}