Integrate alternative frontend

frontend_v2/.gitignore

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+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.js
+
+# testing
+/coverage
+
+# production
+/build
+
+# misc
+.DS_Store
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*

frontend_v2/Makefile

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+define INFO_MSG
+----------------------
+Install and launch the frontend app:
+
+> npm install
+> npm start
+
+----------------------
+A few useful commands:
+
+Get the PID of the processes running on port 3000:
+> lsof -i :3000
+
+Kill the process given the PID:
+> kill -9 PID
+
+endef
+
+export INFO_MSG
+info:
+	@echo "$$INFO_MSG"
+
+.PHONY: info

frontend_v2/README.md

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+# Step-by-step coding of the frontend
+
+Are you new to JavaScript, React and Pixi?  
+Do you want to contribute or simply understand the code powering the visual frontend of `tqecjs`?  
+Look no further.  
+
+In this folder we will re-build the frontend adding a few lines of codes at a time.
+The commit message will make clear which functionality is added (or, at least, the goal is to have informative commits).
+
+**NOTE:** The step-by-step frontend does not exactly match the official one in the `<repo>/frontend` folder.
+This helps to better understand certain design choices while at the same time providing a playground for alternatives.
+
+
+
+## Installation and execution
+
+From this folder, install by typing:
+```bash
+npm start
+```
+
+Run the app in the development mode by typing:
+```bash
+npm start
+```
+Open [http://localhost:3000](http://localhost:3000) to view it in your browser.
+
+The page will reload when you make changes.  
+You may also see any lint errors in the console.
+
+Launch the test runner in the interactive watch mode.
+```bash
+npm test
+```
+See the section about [running tests](https://facebook.github.io/create-react-app/docs/running-tests) for more information.
+
+Build the app for production to the `build` folder:
+```bash
+npm run build
+```
+It correctly bundles React in production mode and optimizes the build for the best performance.
+
+The build is minified and the filenames include the hashes.  
+Your app is ready to be deployed!  
+See the section about [deployment](https://facebook.github.io/create-react-app/docs/deployment) for more information.
+
+
+
+## Learn More
+
+You can learn more in the [Create React App documentation](https://facebook.github.io/create-react-app/docs/getting-started).
+
+To learn React, check out the [React documentation](https://reactjs.org/).