Ensure proper handling of hx attributes

[egil]

If the value in hx attributes contains certain characters used in javascript, these are escaped by default by the renderer. That breaks functionality.

• Enable easy serialization of object into hx-header and hx-vals attributes, such that the JSON is correctly embedded in the markup.
• Ensure hx attributes values are escaped as expected.

Attributes that contains JSON or JavaScript

• https://htmx.org/attributes/hx-on/
• https://htmx.org/attributes/hx-vals/
• https://htmx.org/attributes/hx-headers/

[egil]

Looks like all basic cases work. Users just need to choose either single or double quotes around the attribute value, and then use the opposite inside the value for the json properties and values.