Add example: Not Knot!

Related to satwikkansal#1

Author: satwikkansal

README.md

@@ -1451,6 +1451,35 @@ tuple()
 
 ---
 
+### not knot!
+
+Suggested by @MostAwesomeDude in [this](https://github.com/satwikkansal/wtfPython/issues/1) issue.
+
+```py
+x = True
+y = False
+```
+
+**Output:**
+```py
+>>> not x == y
+True
+>>> x == not y
+  File "<input>", line 1
+    x == not y
+           ^
+SyntaxError: invalid syntax
+```
+
+#### 💡 Explanation:
+
+* Operator precedence affects how an expression is evaluated, and `==` operator has higher precedence than `not` operator in Python.
+* So `not x == y` is equivalent to `not (x == y)` which is equivalent to `not (True == False)` finally evaluating to `True`.
+* But `x == not y` raises a `SyntaxError` because it can be thought of being equivalent to `(x == not) y` and not `x == (not y)` which you might have expected at first sight.
+* The parser expected the `not` token to be a part of the `not in` operator (because both `==` and `not in` operators have same precedence), but after not being able to find a `in` token following the `not` token, it raises a `SyntaxError`.
+
+---
+
 ### Loop variable resilient to changes
 
 Suggested by @tukkek in [this](https://github.com/satwikkansal/wtfPython/issues/11) issue.