Add a few symbols to the math dialog menu

Change-Id: Id9fdbde64957af149784bb16ac225e3896bb9b8d

modules/ve-math/mathSymbols.json

@@ -1468,6 +1468,24 @@
         },
         {
             "insert": "\\twoheadleftarrow"
+        },
+        {
+            "contain": true,
+            "tex": "\\xrightarrow[b]{a}",
+            "encapsulate": {
+                "pre": "\\xrightarrow[",
+                "placeholder": "b",
+                "post": "]{a}"
+            }
+        },
+        {
+            "contain": true,
+            "tex": "\\xleftarrow[b]{a}",
+            "encapsulate": {
+                "pre": "\\xleftarrow[",
+                "placeholder": "b",
+                "post": "]{a}"
+            }
         }
     ],
     "math-visualeditor-symbol-group-math-special": [
@@ -2132,6 +2150,14 @@
         },
         {
             "insert": "\\rceil"
+        },
+        {
+            "tex": "\\lfloor x \\rceil",
+            "encapsulate": {
+                "pre": "\\lfloor ",
+                "placeholder": "x",
+                "post": " \\rceil"
+            }
         }
     ],
     "math-visualeditor-symbol-group-math-matrices": [
@@ -2693,6 +2719,11 @@
             "insert": "\\underbrace{ a+b+\\cdots+z }_{26}",
             "largeLayout": true,
             "width": "wide"
+        },
+        {
+            "insert": "{}_pF_q\\left({a_1, \\ldots, a_p \\atop b_1, \\ldots, b_q}; z\\right)",
+            "largeLayout": true,
+            "width": "wide"
         }
     ]
 }