Added readthedocs config file (#417)

Author: czgdp1807

.readthedocs.yaml

@@ -0,0 +1,15 @@
+version: 2
+
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.8"
+
+sphinx:
+   configuration: docs/conf.py
+
+python:
+   install:
+   - requirements: docs/requirements.txt
+   - method: pip
+     path: .

pydatastructs/trees/binary_trees.py

@@ -420,8 +420,8 @@ def rank(self, x):
         its index in the sorted list of nodes
         of the tree.
 
-        Parameter
-        =========
+        Parameters
+        ==========
 
         x: key
             The key of the node whose rank is to be found out.
@@ -441,8 +441,8 @@ def _simple_path(self, key, root):
         """
         Utility funtion to find the simple path between root and node.
 
-        Parameter
-        =========
+        Parameters
+        ==========
 
         key: Node.key
             Key of the node to be searched