docs: mention 'npm run snap'

docs/src/content/docs/api/snapshot-testing/index.md

@@ -71,9 +71,33 @@ Asserts:  1 passed, of 1
 Time:     422ms
 ```
 
-By setting `TAP_SNAPSHOT` in the environment, we tell tap to write the
-output to a special file, and treat the assertion as automatically
-passing.
+By setting `TAP_SNAPSHOT` in the environment or passing the `--snapshot`
+command line flag, we tell tap to write the output to a special file, and
+treat the assertion as automatically passing.
+
+Snapshots will be generated by default if the npm script being run is named
+`snap` or `snapshot`, so you can use this pattern to test and snapshot most
+projects:
+
+```json
+{
+  "name": "my-project",
+  "version": "1.2.3",
+
+  "devDependencies": {
+    "tap": "15"
+  },
+  "scripts": {
+    "test": "tap",
+    "snap": "tap"
+  }
+}
+```
+
+Then, you can use `npm test` to run your tests, or `npm run snap` to
+update snapshot files.
+
+## Snapshot Files
 
 The [generated file](/snapshot-example/tap-snapshots/test.js-TAP.test.js)
 is designed to be human-readable, but you should not edit it directly.