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

resources/resource_transformers/tocss/dartsass/client.go

@@ -135,7 +135,7 @@ type Options struct {
 	// Vars will be available in 'hugo:vars', e.g:
 	//     @use "hugo:vars";
 	//     $color: vars.$color;
-	Vars map[string]string
+	Vars map[string]any
 }
 
 func decodeOptions(m map[string]any) (opts Options, err error) {