add script to merge scratch-gui deps

This is in preparation for having webpack build scratch-gui source
instead of consuming its build output. This script merges the
dependencies listed in package-deps.json with those listed in
scratch-gui's package.json, using the package-deps.json version in case
of conflict, then writes the result into the `devDependencies` section
of scratch-desktop's package.json.

package-deps.json

@@ -0,0 +1,24 @@
+{
+  "description": "Deps of scratch-desktop that don't match scratch-gui. See scripts/rebuild-deps.js",
+  "devDependencies": {
+    "async": "^3.2.0",
+    "babel-plugin-react-intl": "^7.5.7",
+    "copy-webpack-plugin": "^5.1.1",
+    "electron": "^8.2.5",
+    "electron-builder": "^22.6.0",
+    "electron-devtools-installer": "^3.0.0",
+    "electron-notarize": "^0.3.0",
+    "electron-store": "^5.1.1",
+    "electron-webpack": "^2.8.2",
+    "eslint": "^7.0.0",
+    "eslint-config-scratch": "^6.0.0",
+    "eslint-plugin-import": "^2.20.0",
+    "eslint-plugin-react": "^7.20.0",
+    "mkdirp": "^1.0.4",
+    "nets": "^3.2.0",
+    "rimraf": "^3.0.2",
+    "scratch-gui": "github:LLK/scratch-gui#scratch-desktop",
+    "source-map-loader": "^0.2.4",
+    "uuid": "^8.0.0"
+  }
+}

scripts/rebuild-deps.js

@@ -0,0 +1,26 @@
+const fs = require('fs');
+
+const desktopPackage = require('../package.json');
+const desktopRawPackage = require('../package-deps.json');
+const guiPackage = require('../node_modules/scratch-gui/package.json');
+
+const sortObject = obj => Object
+    .keys(obj)
+    .sort()
+    .reduce(
+        (accumulator, currentKey) => {
+            accumulator[currentKey] = obj[currentKey];
+            return accumulator;
+        },
+        {}
+    );
+
+desktopPackage.devDependencies = sortObject(Object.assign(
+    {},
+    guiPackage.devDependencies,
+    desktopRawPackage.devDependencies
+));
+
+let newDesktopPackage = JSON.stringify(desktopPackage, null, 2);
+newDesktopPackage += '\n';
+fs.writeFileSync('package.json', newDesktopPackage);