docs: adds note about subfolders to history mode samples (vuejs#2954)

* Adds note on subfolders to history mode samples

fixes vuejs#2863

* Be a little more explicit in history mode guide

* Adds missing full stop.

Author: AVGP

docs/guide/essentials/history-mode.md

@@ -19,6 +19,8 @@ Not to worry: To fix the issue, all you need to do is add a simple catch-all fal
 
 ## Example Server Configurations
 
+**Note**: The following examples assume you are serving your app from the root folder. If you deploy to a subfolder, you should use [the `publicPath` option of Vue CLI](https://cli.vuejs.org/config/#publicpath) and the related [`base` property of the router](https://router.vuejs.org/api/#base). You also need to adjust the examples below to use the subfolder instead of the root folder (e.g. replacing `RewriteBase /` with `RewriteBase /name-of-your-subfolder/`).
+
 #### Apache
 
 ```apache