Update README.md

Author: pensivebrian

doc/installation/README.md

@@ -4,7 +4,7 @@
 
 Select your platform for mssql-cli installation instructions:
 
-| [Windows](https://github.com/dbcli/mssql-cli/blob/master/doc/installation/windows.md#windows-installation) | [macOS](https://github.com/dbcli/mssql-cli/blob/master/doc/installation/macos.md#macos-installation) | [Linux](https://github.com/dbcli/mssql-cli/blob/master/doc/installation/linux.md) |
+| [Windows](https://github.com/dbcli/mssql-cli/blob/master/doc/installation/windows.md#windows-installation) (preview)| [macOS](https://github.com/dbcli/mssql-cli/blob/master/doc/installation/macos.md#macos-installation) | [Linux](https://github.com/dbcli/mssql-cli/blob/master/doc/installation/linux.md) |
 | - | - | - |