docs(browsers): add documentation describing managing browsers (#1907)

Author: aslushnikov

docs/README.md

@@ -58,4 +58,5 @@
     - Storybooks
 1. [Extensibility](./extensibility.md)
     - [Custom selector engines](./extensibility.md#custom-selector-engines)
+1. [Managing browser binaries](./browsers.md)
 1. [API Reference](./api.md)

docs/browsers.md

@@ -0,0 +1,83 @@
+# Managing browser binaries
+
+Playwright comes bundled with browsers, and by default `npm i playwright` downloads
+all 3 browsers inside the `node_modules/` folder. This way no extra steps are needed
+to get playwright up and running.
+
+However, Playwright also has rich configuration to support various strategies
+for browser management.
+
+## Download from artifact repository
+
+By default, Playwright downloads browsers from Microsoft and Google public CDNs.
+
+Sometimes companies maintain an internal artifact repository to host browser
+binaries. In this case, Playwright can be configured to download from a custom
+location using the `PLAYWRIGHT_DOWNLOAD_HOST` env variable.
+
+```sh
+$ PLAYWRIGHT_DOWNLOAD_HOST=192.168.1.78 npm i playwright
+```
+
+## Share browser binaries across projects
+
+Sometimes developers work with multiple NPM projects that all use Playwright.
+By default, every project will have browser binaries in its own `node_modules/` folder.
+To save some HDD space and to speedup installation, Playwright can re-use
+browser binaries.
+
+Sharing browser binaries is a two-step process:
+
+1. When installing Playwright, ask it to download browsers into a shared location:
+
+```sh
+$ PLAYWRIGHT_BROWSERS_PATH=$HOME/pw-browsers npm i playwright
+```
+
+2. When running Playwright scripts, ask it to search for browsers in a shared location:
+
+```sh
+$ PLAYWRIGHT_BROWSERS_PATH=$HOME/pw-browsers node playwright-script.js
+```
+
+> **NOTE** Developers can opt-in in this mode via exporting `PLAYWRIGHT_BROWSERS_PATH=$HOME/pw-browsers` in their `.bashrc`.
+
+## Completely avoid browser installation
+
+In certain cases, it is desired to avoid browser installation altogether because
+browser binaries are managed separately.
+
+This can be done by setting `PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD` variable before installation.
+
+```sh
+$ PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD=1 npm i playwright
+```
+
+## Download single browser binary
+
+Playwright ships three packages that bundle only a single browser:
+- [`playwright-chromium`](https://www.npmjs.com/package/playwright-chromium)
+- [`playwright-webkit`](https://www.npmjs.com/package/playwright-webkit)
+- [`playwright-firefox`](https://www.npmjs.com/package/playwright-firefox)
+
+> **NOTE** All configuration environment variables also apply to these packages.
+
+Using these packages is as easy as using a regular Playwright:
+
+1. Install a specific package
+
+```sh
+$ npm i playwright-webkit
+```
+
+2. Requre package
+
+```js
+// Notice a proper package name in require
+const {webkit} = require('playwright-webkit');
+
+(async () => {
+  const browser = await webkit.launch();
+  // ....
+})();
+```