Expose available formatters in the Node API

docs/developer-guide/formatters.md

@@ -31,3 +31,7 @@ A formatter is a function that accepts *an array of these stylelint result objec
   ignored: false // This is `true` if the file's path matches a provided ignore pattern
 }
 ```
+
+## `stylelint.formatters`
+
+stylelint's internal formatters are exposed publicly in `stylelint.formatters`.

lib/__tests__/formatters.test.js

@@ -0,0 +1,7 @@
+"use strict"
+
+const stylelint = require("..")
+
+it("formatters are exposed on stylelint object", () => {
+  expect(typeof stylelint.formatters.json).toBe("function")
+})

lib/index.js

@@ -8,6 +8,7 @@ const createRuleTester = require("./testUtils/createRuleTester")
 const createStylelint = require("./createStylelint")
 const postcssPlugin = require("./postcssPlugin")
 const rules = require("./rules")
+const formatters = require("./formatters")
 const standalone = require("./standalone")
 
 const api = postcssPlugin
@@ -20,6 +21,7 @@ api.utils = {
 
 api.lint = standalone
 api.rules = rules
+api.formatters = formatters
 api.createPlugin = createPlugin
 api.createRuleTester = createRuleTester
 api.createLinter = createStylelint