Also escape % in URLs.

This improves the fix to #9017 in commit
7c4354646b

An alternative would be to avoid backslash escaping `#` and `%`
in URLs, and instead always add `fragile` to the slide environment.

src/Text/Pandoc/Writers/LaTeX/Util.hs

@@ -94,9 +94,12 @@ stringToLaTeX context zs = do
     in case x of
          '\\'| isUrl -> emitc '/' -- NB. / works as path sep even on Windows
          '#' | isUrl -> emits "\\#" -- see #9014
+         '%' | isUrl -> emits "\\%" -- see #9014
          c | isUrl ->
              if c `elem` ['{', '}', '|', '^', '~', '[', ']', '`']
-                then emits (escapeURIString (const False) [c])
+                then do
+                  emitc '\\'  -- escape the % see #9014
+                  emits (escapeURIString (const False) [c])
                 else emitc c
          '{' -> emits "\\{"
          '}' -> emits "\\}"

test/command/5340.md

@@ -8,7 +8,7 @@
 ^D
 \url{https://example.com/foo-bar}
 \url{https://example.com/foo--bar}
-\url{https://example.com/foo%2Dbar}
-\url{https://example.com/foo%2D%2Dbar}
-\url{https://example.com/foo%2D%2Dbar}
+\url{https://example.com/foo\%2Dbar}
+\url{https://example.com/foo\%2D\%2Dbar}
+\url{https://example.com/foo\%2D\%2Dbar}
 ```