Tailwind is a CSS framework which allows you rapidly build custom user interfaces. As opposed to frameworks like Bootstrap, Bulma and Foundation, it is not a UI Kit. It has no theme or components, but instead allow you to construct your own components by combining a bunch of CSS utilities. So for example, instead of supplying you with a Card component, you can build your own Card by applying the Tailwind CSS styles to a combination of HTML elements.
For the client side development of Geotoast, I have decided to go for Vue.js rather than Angular or React. I have no specific rationale for it other than that from everything I have seen about Vue so far it just seems to make more sense to me than both Angular or React. Vue does not get nearly the amount of attention that Angular or React does, but it still has a flourishing community and plentiful resources are available for learning Vue.