Simplified MathJax

Rather than generating script tags, this now simply wraps suitable
delimiters around the maths, which MathJax will then find.  This is
essentially because I could not work out how to make the script tags
work with MatJax 3.

In fact I can't work out how the script tags ever worked: there doesn't
seem to be any mention of embedding maths this way even for MathJax 2:
all the focus is on using delimiters which MathJax looks for.

In both MathJax 2 and 3 this makes the output look nicer: using the
script approach seems to result in maths which, unless you apply
additional styling, is blue, while this approach results in maths which
is just ordinary.

This change

- only changes the output when using MathJax;
- makes the output simpler in that case;
- makes the formatted output better-looking I think;
- works with at least MathJax 2 as well as 3.

markdown/parse.rkt

@@ -637,14 +637,12 @@
 (define $math-jax-inline
   (try (pdo (string "\\\\(")
             (xs <- (many1Till $anyChar (try (string "\\\\)"))))
-            (return `(script ([type "math/tex"])
-                             ,(list->string xs))))))
+            (return (string-append "\\(" (list->string xs) "\\)")))))
 
 (define $math-jax-display
   (try (pdo (string "\\\\[")
             (xs <- (many1Till $anyChar (try (string "\\\\]"))))
-            (return `(script ([type "math/tex; mode=display"])
-                             ,(list->string xs))))))
+            (return (string-append "\\[" (list->string xs) "\\]")))))
 
 (define $math-jax
   (<or> $math-jax-inline

markdown/test.rkt

@@ -930,11 +930,9 @@
                       (!HTML-COMMENT () " more")))))
   ;; https://github.com/greghendershott/markdown/issues/52
   (check-md "\\\\(ax^2 + bx + c = 0\\\\)"
-            '((p () (script ((type "math/tex"))
-                            "ax^2 + bx + c = 0"))))
+            '((p () "\\(ax^2 + bx + c = 0\\)")))
   (check-md "\\\\[ax^2 + bx + c = 0\\\\]"
-            '((p () (script ((type "math/tex; mode=display"))
-                            "ax^2 + bx + c = 0"))))
+            '((p () "\\[ax^2 + bx + c = 0\\]")))
   ;; but single \ still escapes as usual and the contents are still
   ;; parsed as markdown:
   (check-md "\\(some *italic* text\\)"