tocss: Simplify the hugo:vars type handling

Instead of maintaing a list of all CSS units and functions this commit:

* Uses 3 regexps to detect typed CSS values (e.g. `24px`) + properly handle numeric Go types.
* These regexps may have some false positives -- e.g. strings that needs to be quoted.
* For that rare case, you can mark the string with e.g. `"32xxx" | css.Quoted`
* For the opposite case:  `"32" | css.Unquoted`

Updates #10632

tpl/css/css.go

@@ -0,0 +1,41 @@
+package css
+
+import (
+	"github.com/gohugoio/hugo/common/types/css"
+	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/tpl/internal"
+	"github.com/spf13/cast"
+)
+
+const name = "css"
+
+// Namespace provides template functions for the "css" namespace.
+type Namespace struct {
+}
+
+// Quoted returns a string that needs to be quoted in CSS.
+func (ns *Namespace) Quoted(v any) css.QuotedString {
+	s := cast.ToString(v)
+	return css.QuotedString(s)
+}
+
+// Unquoted returns a string that does not need to be quoted in CSS.
+func (ns *Namespace) Unquoted(v any) css.UnquotedString {
+	s := cast.ToString(v)
+	return css.UnquotedString(s)
+}
+
+func init() {
+	f := func(d *deps.Deps) *internal.TemplateFuncsNamespace {
+		ctx := &Namespace{}
+
+		ns := &internal.TemplateFuncsNamespace{
+			Name:    name,
+			Context: func(args ...any) (any, error) { return ctx, nil },
+		}
+
+		return ns
+	}
+
+	internal.AddTemplateFuncsNamespace(f)
+}