Note on Administrator rights for Windows PG deployment (#359)

* Note on Administrator rights for Windows PG deployment

* test with warning

* better warning

* Update README.md

Co-authored-by: Gary Hsu <[email protected]>

* error msg

Co-authored-by: Cedric Guillemet <[email protected]>
Co-authored-by: Gary Hsu <[email protected]>

Author: 3 people

README.md

@@ -54,6 +54,11 @@ npm run select 0.64
 ```
 Selecting the React Native install will also install all NPM packages and its dependencies for the Playground sample/test app.
 
+> :warning: When setting up the Playground app for UWP, the `npm run select` command must be run with Administrator rights, because of the symbolic links. Not doing so will result in this build error will popup when trying to run the Playground:
+```
+ The path cannot be traversed because it contains an untrusted mount point.
+ ```
+
 This will also automatically do the following to prepare your repo for development:
 
 - Update git submodules to fetch Babylon Native and its dependencies