Improve COVIDNet-UI Code Consistency + Style

[rahmatkhah]

The code base is very inconsistent and the original codebase did not follow the best practices of React web development.

• Install & Configure ESLint
• Make file names consistent with React naming conventions (See here for more details.)
• Resolve CSS warnings
• Resolve HTML warnings
• Resolve TypeScript Async Code and Promises Warnings
• Resolve TypeScript Code Formatting
• Resolve TypeScript Control Flow Issues
• Resolve TypeScript Data Flow Issues
• Resolve ES6 issues
• Resolve import and dependency warnings
• Remove unused TypeScript symbols
• Refactor code to use consistent single/double quotes, semi-colons, commas, indentations/spacing
• Use proper TypeScript typing
• Consistent file-naming
• Implement prettier into project
• Follow consistent best React practices for passing props, defining components, etc
• Consistent naming for variable names (e.g. for reducer and context values, all caps for constants)