Documentation for target browsers (#2634)

README.md

@@ -399,7 +399,7 @@ When compiling assets for production on a remote server, such as a continuous in
   - [Webpack-dev-server](./docs/webpack-dev-server.md)
   - [Environment Variables](./docs/env.md)
   - [Folder Structure](./docs/folder-structure.md)
-  - [Assets](./docs/assets.md) - [CSS, Sass and SCSS](./docs/css.md) - [ES6](./docs/es6.md)
+  - [Assets](./docs/assets.md) - [CSS, Sass and SCSS](./docs/css.md) - [ES6](./docs/es6.md), [Target browsers](./docs/target.md)
     - [Props](./docs/props.md)
     - [Typescript](./docs/typescript.md)
   - [Yarn](./docs/yarn.md)

docs/target.md

@@ -0,0 +1,22 @@
+# Target browsers
+
+By default webpacker provides these front-end tools:
+- [@babel/preset-env](https://github.com/babel/babel/tree/master/packages/babel-preset-env)
+- [Autoprefixer](https://github.com/postcss/autoprefixer)
+- [postcss-preset-env](https://github.com/csstools/postcss-preset-env)
+
+All these tools use [Browserslist](https://github.com/browserslist/browserslist) to detect which environment your users have
+
+Webpacker browserslist default target:
+```
+defaults
+```
+
+`defaults`: `(> 0.5%, last 2 versions, Firefox ESR, not dead)`, [browserl.ist](https://browserl.ist/) is an online tool to check what browsers will be selected by some query.
+
+To keep browsers data up to date, you need to run:
+```bash
+yarn upgrade caniuse-lite
+```
+
+at least once every few months, to prevent such [problems](https://github.com/browserslist/browserslist/issues/492)