fix: isBrowser() to include check on window (#982)

There are several checks in `GoTrueClient.ts` that check
`window?.[prop]` after checking `isBrowser()` which throws an error in
node environments that have `document` defined but not `window`.

Fixes:

- supabase/supabase-js#786

src/lib/helpers.ts

@@ -14,7 +14,8 @@ export function uuid() {
   })
 }
 
-export const isBrowser = () => typeof document !== 'undefined'
+export const isBrowser = () =>
+  typeof window !== 'undefined' && typeof document !== 'undefined'
 
 const localStorageWriteTests = {
   tested: false,