Add buttons documentation

- Add documentation for how to use buttons
- Update markup and CSS rulesets to support icons on the left or the
right of text

Signed-off-by: Derick Montague <derick.montague@ibm.com>
Change-Id: Ic897f416e85824287360bc7ef5dc47c402d64eba
diff --git a/docs/.vuepress/config.js b/docs/.vuepress/config.js
index 5a8e601..2be074e 100644
--- a/docs/.vuepress/config.js
+++ b/docs/.vuepress/config.js
@@ -42,7 +42,10 @@
           },
           {
             title: "Components",
-            children: ["/guide/components/", "/guide/components/page-section"]
+            children: [
+            "/guide/components/",
+            "/guide/components/button",
+          ]
           }
         ],
         "/themes/": [""]