Fixes Issue #211: Adding Functionality to The Loading Indicator

[teamomiamigo]

This pull request adds a loading indicator on the login button during the login process. The changes include:

• Added a loading state using React's useState hook to track the login process.
• Updated the onLoginPress function to set loading to true at the start of the login process and back to false after the process completes.
• Conditionally render an ActivityIndicator on the login button when loading is true.
• Ensure that the button is responsive to user interactions.
• Removes a time delay on the login to make more seamless and faster logging in
  Files Changed:
  LoginScreen.tsx