Add optional ReadableStream polyfill

index.js

@@ -2,6 +2,15 @@
 const fetch = require('node-fetch');
 const AbortController = require('abort-controller');
 
+// Extracted from https://github.com/Richienb/try-import/blob/master/index.js
+function tryImport(name) {
+	try {
+		return require(name);
+	} catch (_) { }
+}
+
+const streams = tryImport('web-streams-polyfill/ponyfill/es2018');
+
 if (!global.fetch) {
 	global.fetch = fetch;
 }
@@ -22,4 +31,8 @@ if (!global.AbortController) {
 	global.AbortController = AbortController;
 }
 
+if (!global.ReadableStream && streams) {
+	global.ReadableStream = streams.ReadableStream;
+}
+
 module.exports = require('ky/umd');

package.json

@@ -64,6 +64,9 @@
 	"peerDependencies": {
 		"ky": ">=0.17.0"
 	},
+	"optionalDependencies": {
+		"web-streams-polyfill": ">=2.0.0"
+	},
 	"browser": "browser.js",
 	"ava": {
 		"register": [

readme.md

@@ -23,6 +23,8 @@ $ npm install ky ky-universal
 
 *Note that you also need to install `ky`.*
 
+For `ReadableStream` support, also install [`web-streams-polyfill`](https://github.com/MattiasBuelens/web-streams-polyfill).
+
 ## Usage
 
 ```js