Mindey, 
Package manager (e.g. NPM) for shared libraries in browser
Make browser user able to install libraries, like on operating system, and reduce the amount of data that we have to download for each app loading.
Today, each web application packages all its dependencies (often a very deep npm tree), every time we open it. A large number of JavaScript libraries are the same (e.g., ReactJS, Bootstrap, @fortawesome/fontawesome-svg-core, node-sass, etc. etc.) they don't need to be loaded for each website, or web app. The browser could provide the shared dependencies, that all web apps could use.
If the browser would have these libraries shared, then we wouldn't have to use so much traffic to load them from every app every time, that would reduce the traffic footprint for downloading app dependencies.
+[project]
This is similar to an idea I had for native libraries.
These are libraries that have JavaScript equivalents that can be transparently replaced with native code without any JavaScript overhead.
Would be useful for game engines, crypto and anything computationally expensive.
https://github.com/samsquire/ideas#51-native-web-libraries