docs: add note about win64 build

scripts/make-win64.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+pushd "$(dirname "${BASH_SOURCE[0]}")/../"
+
+dl_file() {
+    local FILE="$1"
+    if [[ ! -f "$FILE" ]]; then
+        curl -fsL "https://um-react.app/files/${FILE}.gz" | gzip -d >"${FILE}"
+    fi
+}
+
+dl_file "um-react-wry-builder-0.1.0-linux-amd64"
+dl_file "um-react-wry-stub-0.1.0-win64.exe"
+chmod a+x um-react-wry-builder-0.1.0-linux-amd64
+
+APP_VERSION="$(jq -r '.version' <package.json)"
+./um-react-wry-builder-0.1.0-linux-amd64 \
+    -t um-react-wry-stub-0.1.0-win64.exe \
+    -r um-react.zip \
+    -o "um-react-win64-${APP_VERSION}.exe"
+
+echo "Built 'um-react-win64-${APP_VERSION}.exe'."
+
+popd