added code description to the main branch

Author: sabajamalian

README.md

@@ -1,7 +1,7 @@
 # BankAccount
 This is an educational public repository to illustrate the power of automated testing through Github Actions.
 
-# Run locally
+## Run locally
 1. Set up Python virtual environment.
 ```
 python -m venv venv
@@ -17,4 +17,18 @@ python -m pytest
 4. Run the app.
 ```
 python app.py
-```
+```
+
+## Code Description
+
+1. app.py: A flask application that exposes the following API endpoints: 
+  - index at / : Retun a JSON data structure indicating the current balance. 
+  - deposit at /deposit : Take the deposit amount as a URL parameter and return the new balance after adding the amount. 
+  - withdraw at /withdraw : Take the withdrawal amount as a URL parameter and return the new balance after subtracting the amount. 
+App relies on a global in-memory variable (`balance`) to store the balance of the account.
+
+2. requirements.txt: A text file including all the Python libraries and packages needed to run the app. 
+
+3. .gitignore: Refer to the gitignore article for more details. In short, this file makes it possible that local configuration or binary files are not pushed to the repository. 
+
+4. tests: It's a directory that includes several unit tests for the APIs. The tests utilize the PyTest library.