Document $ARGS and friends

docs/content/3.manual/manual.yml

@@ -217,6 +217,9 @@ sections:
         `value` will be treated as a string, so `--arg foo 123` will
         bind `$foo` to `"123"`.
 
+        Named arguments are also available to the jq program as
+        `$ARGS.named`.
+
       * `--argjson name JSON-text`:
 
         This option passes a JSON-encoded value to the jq program as a
@@ -239,6 +242,16 @@ sections:
         one text, then that is used, else an array of texts is used as
         in `--slurpfile`.)
 
+      * `--args`:
+
+        Remaining arguments are positional string arguments.  These are
+        available to the jq program as `$ARGS.positional[]`.
+
+      * `--jsonargs`:
+
+        Remaining arguments are positional JSON text arguments.  These
+        are available to the jq program as `$ARGS.positional[]`.
+
       * `--run-tests [filename]`:
 
         Runs the tests in the given file or standard input.  This must