Created a file for the insert method (#26496)

* Created a file for the insert method

I tried to adopt your style of making these files in order to retain consistency.

* Rename list-insert-method to list-insert-method.md

* Rename guide/english/python/lists/list-insert-method.md to guide/english/python/lists/list-insert-method/index.md

* Added code formatting, changed more info link

guide/english/python/lists/list-insert-method/index.md

@@ -0,0 +1,23 @@
+---
+title: List Insert Method
+---
+## List Insert Method
+
+The method `insert(i,x)` inserts a given value `x` into the list at index `i`. The index must be within the bounds of the list 
+(from `0` to the length of the list minus 1).
+
+#### Example Usage
+
+```py
+numbers = [1, 2, 3, 4, 5]
+numbers.insert(3,8)
+print(numbers)
+```
+#### Output
+```
+[1, 2, 3, 8, 4, 5]
+```
+The value `8` is inserted into the list at position `3`.
+
+#### More Information:
+- [Python Docs: Lists](https://docs.python.org/3.6/tutorial/datastructures.html#more-on-lists)