Added backslashes to descriptions with '[][]'

Changes were made to line 2037, in the case where a node is valType info_array in the JSON with dimension: 2 (eg. groups in _node.py line 137).
This fixes the issue where markdown interprets it as a hyperlink. This line adds '[][]' to the description after the description passed in the JSON file as part of the validation process.
Now, markdown correctly interprets the brackets as consecutive brackets instead.

Author: daexs

_plotly_utils/basevalidators.py

@@ -2034,7 +2034,7 @@ def description(self):
 """.format(el_desc=el_desc)
 
             if self.dimensions in ("1-2", 2):
-                item_validator.plotly_name = "{name}[i][j]".format(
+                item_validator.plotly_name = "{name}\\[i\\]\\[j\\]".format(
                     name=self.plotly_name
                 )