chore: add support for github codespaces

.devcontainer/devcontainer.json

@@ -0,0 +1,13 @@
+{
+  "name": "Super Productivity Dev Container",
+  "image": "mcr.microsoft.com/devcontainers/javascript-node:20",
+  "postCreateCommand": "npm i -g @angular/cli && npm i",
+  "postStartCommand": "ng serve",
+  "forwardPorts": [4200],
+  "portsAttributes": {
+    "4200": {
+      "label": "Angular Dev Server",
+      "onAutoForward": "openBrowser"
+    }
+  }
+}

README.md

@@ -325,8 +325,18 @@ There are several ways to help.
 
 9. **[Sponsor the project](https://github.com/sponsors/johannesjo)**
 
+### :rocket: Try with GitHub Codespaces
+
+You can develop and run Super Productivity instantly in your browser using [GitHub Codespaces](https://github.com/features/codespaces): no need to install Node.js or any dependencies locally. On the top of the repository page, click on "Code", "Codespaces", and then on the plus button, "Create Codespace".
+
+Your VS Code settings can sync as usual, so your environment feels just like home. The development server starts automatically, and the dev container auto-forwards the port. Open the "Ports" tab and Ctrl+Click the available link to preview your running Super Productivity app.
+
+Further customizations to the Codespaces dev container can be performed by editing the .devcontainers/devcontainers.json file according to the [Codespaces documentation](https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-configuration/introduction-to-dev-containers#creating-a-custom-dev-container-configuration) and the [devcontainers full specification](https://containers.dev/implementors/spec/).
+
 ### Running the development server
 
+If you don't want or cannot use Codespaces for any reason, here are the instructions for local development.
+
 To run the development server you need to have Node installed at least in the version 14. Go to https://nodejs.org for installation instructions.
 
 **Clone repo**