fix: go escape constant attributes

[Robert-Kolmos]

Fixes #624, Go escapes constant attribute strings.

This changes the previous behavior where these strings were treated as go strings. If someone previously had

templ foo() {
    <input pattern="\\s">
}

this will now generate
<input pattern="\\s"/> instead of <input pattern="\s"/> like the current latest version would generate.

[a-h]

Thanks a lot for the contribution. Much appreciated!