fix: document session handling pattern

Author: Igor Muchychka

site/data/index.md

@@ -27,6 +27,7 @@
 
 # Patterns
 
+@import './patterns/session-handling.md'
 @import './patterns/feature-background.md'
 @import './patterns/scenario-outlines.md'
 @import './patterns/page-objects.md'

site/data/patterns/session-handling.md

@@ -0,0 +1,20 @@
+## Session handling
+
+If you test a site which uses cookies, localStorage or sessionStorage its a good practise to clear them after each test case.
+Not doing so will make the test cases not isolated.
+Which can lead to not reliable, failing test where would be very hard to find the root cause of the issue.
+Creating a new webdriver session for every test case is not necessary.
+A proper cleanup and page refresh should be sufficient in most cases.
+As starter you can use the following support code.
+
+```javascript
+const { client } = require('nightwatch-cucumber');
+const { defineSupportCode } = require('cucumber');
+
+defineSupportCode(({ After }) => {
+    After(() => client.execute(`
+      localStorage.clear();
+      sessionStorage.clear();
+    `).deleteCookies().refresh());
+});
+```

site/template/res/main.css

@@ -121,6 +121,7 @@ code {
 pre code {
   font-size: inherit;
   color: inherit;
+  padding: 0;
 }
 
 @media (max-width: 769px) {