Install instructions in FAQ

This comes up from time to time.

Author: badeball

docs/faq.md

@@ -4,6 +4,14 @@
 
 This might be because you're trying to specify `-e / --env` multiple times, but [multiple values should be comma-separated](https://docs.cypress.io/guides/guides/command-line#cypress-run-env-lt-env-gt).
 
+---
+
 ### I get `fs_1.promises.rm is not a function`
 
 Upgrade your node version to at least [v14.14.0](https://nodejs.org/api/fs.html#fspromisesrmpath-options).
+
+---
+
+### I get `spawn cucumber-json-formatter ENOENT`
+
+You need to install `cucumber-json-formatter` **yourself**, as per [documentation](json-report.md).