Include nonce attribute for Content Security Policy

See https://github.com/enhance-dev/enhance-starter-project/issues/12

When a nonce is available, form-elements should include that nonce as an attribute to prevent errors like in this screenshot:

```Refused to apply inline style because it violates the following Content Security Policy directive: "[omitted for brevity]". Either the 'unsafe-inline' keyword, a hash ('sha256-WZ567ntT3BKIFaeoTtOOEdkkOJR5UidQJ809ufOE0zk='), or a nonce ('nonce-...') is required to enable inline execution.```