Migration from tslint to an alternate static analysis tool

Given that [tslint is deprecated](https://github.com/palantir/tslint#tslint) and that it is important to note that tslint does not catch indentation errors as mentioned in an example [here](https://github.com/CATcher-org/CATcher/pull/538#discussion_r563040956)

It will be good to have that we migrate from tslint to another static analysis tool such as [eslint](https://github.com/eslint/eslint) to maintain code quality within our code base.

Start by reviewing the repository's existing TSLint configuration and usage across the TypeScript codebase, then compare the migration options, including ESLint. Done means TSLint has been replaced by an agreed static analysis tool and the code-quality checks include indentation errors.

Written by the indexing model from the issue text.