Refactor scriptlets injection code

Builtin scriptlets are no longer parsed as text-based resources,
they are imported as JS functions, and `toString()` is used to
obtain text-based representation of a scriptlet.

Scriptlet parameters are now passed as function call arguments
rather than by replacing text-based occurrences of `{{i}}`. The
arguments are always string values (see below for exception).

Support for argument as Object has been added. This opens the
door to have scriptlets using named arguments rather than
positional arguments, and hence easier to extend functionality
of existing scriptlets. Example:

    example.com##+js(scriplet, { "prop": "adblock", "value": false, "log": true })

Compatibility with user-provided scriptlets has been preserved.

User-provided scriptlets can benefit some of the changes:

Use the form `function(..){..}` instead of `(function(..){..})();`
in order to received scriptlet arguments as part of function call
-- instead of using `{{i}}`.

If using the form `function(..){..}`, you can choose to receive
an Object as argument -- just be sure that your scriptlet's
parameter is valid JSON notation.

.jshintrc

@@ -2,7 +2,7 @@
 	"browser": true,
 	"devel": true,
 	"eqeqeq": true,
-	"esversion": 9,
+	"esversion": 11,
 	"globals": {
 		"chrome": false,     // global variable in Chromium, Chrome, Opera
 		"globalThis": false,