Add internationalization documentation

- Explains how internationalization makes the OpenBMC Web UI
  multilingual
- Explains the use of vue-i18n

Signed-off-by: Sandeepa Singh <sandeepa.singh@ibm.com>
Change-Id: Ica273814a857f37502b9bb71800de7660d4fa49b
diff --git a/docs/.vuepress/config.js b/docs/.vuepress/config.js
index db0bbeb..ed0035c 100644
--- a/docs/.vuepress/config.js
+++ b/docs/.vuepress/config.js
@@ -36,6 +36,7 @@
             title: "Guidelines",
             children: [
               "/guide/guidelines/colors",
+              "/guide/guidelines/internationalization",
               "/guide/guidelines/motion",
               "/guide/guidelines/typography"
             ]