Add MobX for state management

src/components/App/App.tsx

@@ -1,18 +1,28 @@
 import * as React from "react";
+import { observer } from "mobx-react";
 import "./App.scss";
-
-const reactLogo = require("../../assets/img/react_logo.svg");
+import appState from "../../stores/AppStore";
+import Button from "../Button";
 
 export interface AppProps {
+  appState: {
+    increment: () => string,
+    counter: number
+  };
 }
 
-export default class App extends React.Component<AppProps, undefined> {
-    render() {
-        return (
-            <div className="app__landing">
-                <h1>Aalto-yliopiston sähköinsinöörikilta!</h1>
-                <p>Sähköä, viinaa, naisia.</p>
-            </div>
-        );
-    }
+@observer class App extends React.Component<AppProps, undefined> {
+  constructor(props) {
+    super(props);
+  }
+
+  render() {
+      return <div className="app__landing">
+      <h1>Aalto-yliopiston sähköinsinöörikilta!</h1>
+      <p>Sähköä, viinaa, naisia.</p>
+      <Button onClick={this.props.appState.increment}>{this.props.appState.counter}</Button>
+    </div>;
+  }
 }
+
+export default props => <App appState={appState} {...props} />;

src/components/Button/Button.scss

@@ -0,0 +1,20 @@
+@import "../../index.scss";
+
+.button {
+  -webkit-appearance: none;
+  border-radius: none;
+  padding: 0.5rem 1rem;
+  margin: 0.5rem;
+  border: 2px solid $blue;
+  font-size: 1rem;
+  font-weight: 500;
+
+  &:hover {
+    border: 2px solid $dark-blue;
+  }
+
+  &:active,
+  &:focus {
+    outline: none;
+  }
+}

src/components/Button/Button.tsx

@@ -0,0 +1,16 @@
+import * as React from "react";
+import "./Button.scss";
+
+export interface ButtonProps {
+  onClick: () => void;
+}
+
+export default class Button extends React.Component<ButtonProps, undefined> {
+  render() {
+    return (
+      <button onClick={this.props.onClick} className="button">
+        {this.props.children}
+      </button>
+    );
+  }
+}

src/components/Button/index.ts

@@ -0,0 +1,2 @@
+import Button from "./Button";
+export default Button;

src/stores/AppStore.ts

@@ -0,0 +1,13 @@
+import { observable, action } from "mobx";
+import { observer } from "mobx-react";
+
+class AppStore {
+  @observable counter = 0;
+
+  @action.bound
+  increment() {
+    this.counter += 1;
+  }
+}
+
+export default new AppStore();