feat(spannerlib-node): add Windows support to binding.gyp and build script

Author: surbhigarg92

spannerlib/wrappers/spannerlib-node/binding.gyp

@@ -50,6 +50,17 @@
                 'files': [ '<(module_root_dir)/../../shared/libspanner.so' ]
             }
           ]
+        }],
+        ['OS=="win"', {
+          'libraries': [
+            '<(module_root_dir)/../../shared/libspanner.dll'
+          ],
+          'copies': [
+            {
+                'destination': '<(PRODUCT_DIR)',
+                'files': [ '<(module_root_dir)/../../shared/libspanner.dll' ]
+            }
+          ]
         }]
       ]
     }

spannerlib/wrappers/spannerlib-node/scripts/build-shared-lib.sh

@@ -48,7 +48,7 @@ elif [ "$OS" == "Linux" ]; then
     go build -C "$SHARED_LIB_DIR" -o libspanner.so -buildmode=c-shared shared_lib.go
 elif [ "$OS" == "Windows" ]; then
     echo "Building for Windows..."
-    go build -C "$SHARED_LIB_DIR" -o spannerlib.dll -buildmode=c-shared shared_lib.go
+    go build -C "$SHARED_LIB_DIR" -o libspanner.dll -buildmode=c-shared shared_lib.go
 else
     echo "Unsupported operating system: $OS"
     exit 1