feat(hmr): add hmrUpdate function (#689)

Author: Alexander Vakrilov

hmr/hmr-update.js

@@ -0,0 +1,6 @@
+module.exports = () => {
+    const update = require("../hot");
+    const fileSystemModule = require("tns-core-modules/file-system");
+    const applicationFiles = fileSystemModule.knownFolders.currentApp();
+    update(__webpack_require__["h"](), filename => applicationFiles.getFile(filename));
+}

hmr/index.js

@@ -0,0 +1 @@
+module.exports.hmrUpdate = require("./hmr-update");