feat: migrate unit tests to Jest (#6353)

* config(jest): updated setup
* config(jest): update testMatch to include jsx files
* config(jest): add transformIgnorePatterns
* config(jest): update ignore files that do not work in jest yet
* config: add test:unit-jest to test script

* fix(jest): lint with eslint-plugin-jest

* refactor(jest): move unit test directory
* refactor(mocha): restore mocha tests that fail in jest

* docs(jest): update helpful scripts with test:unit-jest

test/unit/bugs/3199-sanitization-escaping.jsx

@@ -0,0 +1,21 @@
+import React from "react"
+import { render } from "enzyme"
+import Markdown from "components/providers/markdown"
+
+describe("UI-3199: Sanitized Markdown causing code examples to be double escaped", function(){
+  it("should single-escape quotes", function(){
+
+    let str = "" +
+    "This is a test: \n\n" +
+    "    {\"abc\": \"def\"}\n"
+
+    let props = {
+      source: str
+    }
+
+    let el = render(<Markdown {...props}/>)
+
+    expect(el.find("code").first().text()).toEqual("{\"abc\": \"def\"}\n")
+    expect(el.find("code").first().html()).toEqual("{&quot;abc&quot;: &quot;def&quot;}\n")
+  })
+})