to complete the explanation, sketch is a vector-based design tool that has an api for scriptable generation of components. this library lets you generate sketch widgets from react code; i presume that those widgets are then higher-level shapes stored as single entitles in sketch, so that when you update the react code, sketch files that use those components now use the updated versions.
also, from their faq, there is no two-way binding; they do not attempt to extract react code from sketch files. the idea is that the react code is the source of truth.
from a programmer's perspective, sketch is sort of like an exploratory repl where you can play with bits of code (widgets here), composing them into larger functions (sketches), and when you're satisfied with the design you edit your source file and reload the state of the repl so you can continue exploring.
also, from their faq, there is no two-way binding; they do not attempt to extract react code from sketch files. the idea is that the react code is the source of truth.
from a programmer's perspective, sketch is sort of like an exploratory repl where you can play with bits of code (widgets here), composing them into larger functions (sketches), and when you're satisfied with the design you edit your source file and reload the state of the repl so you can continue exploring.