Add update installer program (Windows only for now)

src/updater/CMakeLists.txt

@@ -0,0 +1,12 @@
+add_executable(updater
+  updater.cpp
+  updater.h
+)
+
+target_link_libraries(updater PRIVATE common minizip zlib)
+
+if(WIN32)
+  target_sources(updater PRIVATE
+    win32_main.cpp
+  )
+endif()