Outline fields which are required (bug 1724918)

- it aims to fix https://bugzilla.mozilla.org/show_bug.cgi?id=1724918;

- it applies for both Acroform and XFA.

test/pdfs/.gitignore

@@ -525,4 +525,4 @@
 !issue14862.pdf
 !issue14705.pdf
 !bug1771477.pdf
-
+!bug1724918.pdf

test/test_manifest.json

@@ -6553,5 +6553,12 @@
       "link": true,
       "type": "eq",
       "annotations": true
+   },
+   { "id": "bug1724918",
+      "file": "pdfs/bug1724918.pdf",
+      "md5": "ab30269570c8ff2c9f8eb73fb376a081",
+      "rounds": 1,
+      "type": "eq",
+      "annotations": true
    }
 ]