script: Restrict allowed node types for XPath context node (#39751)

See
https://searchfox.org/firefox-main/rev/b30a9b734819436853abf4eba6d768037514b3f6/dom/xslt/xpath/XPathExpression.cpp#115
for the equivalent code in firefox. Chrome also throws the same error.

Testing: This change adds a test
Part of #34527

---------

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

tests/wpt/mozilla/meta/MANIFEST.json

@@ -13795,6 +13795,13 @@
       {}
      ]
     ],
+    "invalid-xpath-context-nodes.html": [
+     "b306037d7fa8923af92d60a09c5df77e2937e4f6",
+     [
+      null,
+      {}
+     ]
+    ],
     "iterable.html": [
      "d4fe1259b01ccef6f1185f5a3d52f8b014a21d51",
      [