Add test for toggle on mobile size

src/test/rustdoc-gui/toggle-docs-mobile.goml

@@ -0,0 +1,21 @@
+goto: file://|DOC_PATH|/test_docs/struct.Foo.html
+size: (433, 600)
+assert: (".top-doc", "open", "")
+click: (4, 280) // This is the position of the top doc comment toggle
+assert-false: (".top-doc", "open", "")
+click: (4, 280)
+assert: (".top-doc", "open", "")
+// To ensure that the toggle isn't over the text, we check that the toggle isn't clicked.
+click: (3, 280)
+assert: (".top-doc", "open", "")
+
+// Now we do the same but with a little bigger width
+size: (600, 600)
+assert: (".top-doc", "open", "")
+click: (4, 240) // New Y position since all search elements are back on one line.
+assert-false: (".top-doc", "open", "")
+click: (4, 240)
+assert: (".top-doc", "open", "")
+// To ensure that the toggle isn't over the text, we check that the toggle isn't clicked.
+click: (3, 240)
+assert: (".top-doc", "open", "")