Bootstrap is the most popular CSS Framework for developing responsive and mobile-first websites.

SCSS is a preprocessor scripting language that extends the capabilities of CSS by adding features such as variables, nesting, and mixins. It allows developers to write more efficient and maintainable CSS code, and helps to streamline the development process by reducing repetition and increasing reusability.

A UI kit provides developers with a set of reusable components that can be easily integrated into a website or application. These components are pre-designed with consistent styling and functionality, allowing developers to save time and effort in the design and development process. UI kits can be either custom-built or third-party, and often include components for buttons, forms, typography, icons, and more.

ESLint is a linter for JavaScript that analyzes code to detect and report on potential problems and errors, as well as enforce consistent code style and best practices, helping developers to write cleaner, more maintainable code.

RollupJS is a popular and efficient JavaScript module bundler that takes the code from multiple modules and packages them into a single optimized file, minimizing the overall size of the application and improving its performance.