Text string '0x' is marshaled without quotes.

**Describe the bug**

Attempting to marshal the text string `'0x'` returns without quotes.

**To Reproduce**

https://go.dev/play/p/Zu1JcjgLguZ

**Expected behavior**

The text string should be marshalled with quotes, as it is a string.

**Version Variables**
 - Go version: 1.21
 - go-yaml's Version: e.g. v1.15.11
