fix(shared): Use globalThis instead of global in encodeB64 (#7648)

Author: jacekradko

.changeset/tired-oranges-run.md

@@ -0,0 +1,5 @@
+---
+"@clerk/shared": patch
+---
+
+Use `globalThis` instead of `global` in `encodeB64`

packages/shared/src/internal/clerk-js/encoders.ts

@@ -1,5 +1,5 @@
 export function encodeB64(input: string) {
-  return global.btoa(input);
+  return globalThis.btoa(input);
 }
 
 // https://stackoverflow.com/questions/30106476/