correct README.md array with square brackets for sandbox multiple values

[Tim0Cc]

In README.md l.52

it says
"sandbox - add optional sandbox values. For single value, add as string. For multiple values, add as array ({"allow-scripts", "allow-same-origin"}). Valid values are "allow-forms allow-pointer-lock allow-popups allow-same-origin allow-scripts allow-top-navigation""

and should say
"add as array (["allow-scripts", "allow-same-origin"])."
-> with square brackets, not curly brackets