Fix typos in windows installer README (#1217)

Author: joedborg

installer/windows/README.md

@@ -10,13 +10,13 @@ Uses the NSIS package to create the installer.
 
 ### Building
 
-2 files must be places in the working directory before compiling the installer.  These are:
+2 files must be placed in the working directory before compiling the installer.  These are:
 
 * `microk8s.exe`:  This is the file generated by PyInstaller.
 * `multipass.exe`:  This is the Multipass installer exe, which is run at install time.
 
 Use the following command to compile the installer.
 
 ```
-makensis microk8s-windows.nsi
+makensis microk8s.nsi
 ```