Added Toast Notification to make our app more user friendly

Description

In this MR, I have made an improvement to the app by adding toast notifications, which appear whenever certain events occur that users may want to be notified about. These events include adding a new candidate or election, voting, and editing an election. I have added these notifications in places where they are most relevant and necessary to inform users. This enhancement is intended to improve the user experience and make the app more user-friendly.

Fixes # (issue)

• added toast notification

Images for reference

Election Toast Notification

ADD candidate Toast Notification

Failed to add candidate Toast Notification

Vote Successfull Toast Notification

Loading Toast Notification

Type of change

Please mark the options that are relevant.

• Updated UI/UX
• Improved the business logic of code
• Added new feature
• Other

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings