docs(readme): add setup guide & usage example

README.md

@@ -1,2 +1,24 @@
 # stdstream-snapshot
-Weak referenced array
+Tiny util for CLI testing: fetch stdout, stderr streams and match data to snapshot
+
+## Install
+```bash
+yarn add stdstream-snapshot -D
+npm add stdstream-snapshot -D
+```
+
+## Usage
+```javascript
+import {match} from 'stdstream-snapshot'
+
+it('cmd output matches to spapshot', () => {
+  const cmd = 'somecmd --flag=foo -b'
+  const path = './test/snapshots/some-cmd-output.json'  
+
+  expect(match({
+    cmd,
+    path,
+    update: true
+  })).toBeTruthy()
+})
+```