added example documentation

Author: rbtzuniga

lab_04/example_documentation.md

@@ -0,0 +1,25 @@
+# Example API Documentation
+
+## Connecting to the API
+Since we are running our API locally we will access the endpoint at ```http://127.0.0.1:5000``` (or the address the appears on your console).
+
+## Welcome
+- Method: GET
+- Path: ```/```
+- Query parameters: None
+
+This is just a friendly welcome to the API.
+
+## Sum
+- Method: GET
+- Path: ```/sum```
+- Query parameters: two integers ```a``` and ```b```
+
+This query returns the sum of the two numbers in json format.
+
+## Factorial
+- Method: GET
+- Path: ```/factorial```
+- Query parameters: An integer number ```n```
+
+This query display a message with the result of n!. If no number is provided, it takes ```n = 10``` by default.