Windows build: corrected deployment script for RTL-SDR plugin to bundle librtlsdr.dll

windows.install.bat

@@ -3,6 +3,7 @@ SET libusbdir="D:\libusb-1.0.20\MinGW32"
 copy app\%1\sdrangel.exe %2
 copy sdrbase\%1\sdrbase.dll %2
 copy lz4\%1\lz4.dll %2
+copy librtlsdr\%1\librtlsdr.dll %2
 copy %libusbdir%\dll\libusb-1.0.dll %2
 mkdir %2\plugins
 mkdir %2\plugins\channel