DB Connection, gitignore and test_db with mock data

[jcrucesdeveloper]

Short description

• db.py file added and stablish connection using SQLite
• Added file test_db.py to test the connection with DB
• Modified requirements.txt work with streamlit and sqlite
• Created tables users and added mock data to test
• Added .env.example and starting using environment variables instead of hardcoded values

How to test it

Execute: streamlit run test_db.py You should see something like this