Update README

README.md

@@ -90,5 +90,29 @@ $ ./appStore.sh
 
 After that, the `.pkg` file is created under `./packages`.
 
+Please upload the `.pkg` to App Store using Application Loader in Xcode.
+
+### Snapcraft
+
+First, please prepare snapcraft command.
+
+```bash
+$ brew install snapcraft
+```
+
+And prepare docker environment which is used in snapcraft building.
+
+Build app for linux.
+
+```bash
+$ npm run build:linux
+```
+
+And upload.
+
+```bash
+$ snapcraft push build/whalebird_1.0.0_amd64.snap --release stable
+```
+
 # License
 The software is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).