build(convert-touchstone): fix missing devDependency

Author: QuentinRoy

packages/convert-touchstone/package.json

@@ -11,6 +11,7 @@
     "sax": "^1.2.4"
   },
   "devDependencies": {
+    "babel-core": "^6.26.3",
     "babel-plugin-transform-object-rest-spread": "6.26.0",
     "cross-env": "5.2.0",
     "jest": "23.5.0",

yarn.lock

@@ -953,7 +953,7 @@ babel-code-frame@^6.26.0:
     esutils "^2.0.2"
     js-tokens "^3.0.2"
 
-[email protected]:
+[email protected], babel-core@^6.26.3:
   version "6.26.3"
   resolved "https://registry.yarnpkg.com/babel-core/-/babel-core-6.26.3.tgz#b2e2f09e342d0f0c88e2f02e067794125e75c207"
   dependencies: