chore(*): setup generate-changelog npm task

```
npm install --save-dev commander github-url-from-git generate-changelog
```

bin/generate-changelog.js

@@ -0,0 +1,57 @@
+#!/usr/bin/env node
+
+/**
+ * Simple util based on npm package generate-changelog
+ *
+ * Usage: ./generate-changelog.js previousTag currentTag
+ */
+
+const program = require("commander");
+const packageJson = require("../package.json");
+const githubUrlFromGit = require("github-url-from-git");
+const generateChangelog = require("generate-changelog");
+const { exec } = require("child_process");
+
+const githubRepoUrl =
+  (packageJson.repository &&
+    packageJson.repository.url &&
+    githubUrlFromGit(packageJson.repository.url)) ||
+  undefined;
+
+/**
+ * generate-changelog always takes the latest tag as title / date
+ * this patches this little bug and retrieves the exact date of the targetted tag
+ */
+const retrieveGitTagDate = tag =>
+  new Promise((res, rej) => {
+    exec(`git show -s --format=%ci ${tag}^{commit}`, (error, stdout) => {
+      if (error) {
+        return rej(error);
+      }
+      return res(stdout);
+    });
+  });
+
+program
+  .usage("<previousTag> <currentTag>")
+  .command("* <previousTag> <currentTag>")
+  .action((previousTag, currentTag) => {
+    const githubDiffLink = `Diff: ${githubRepoUrl}/compare/${previousTag}...${currentTag}`;
+
+    Promise.all([
+      generateChangelog.generate({
+        tag: `${previousTag}...${currentTag}`,
+        repoUrl: githubRepoUrl
+      }),
+      retrieveGitTagDate(currentTag)
+    ]).then(([changelog, currentTagDate]) => {
+      console.log(
+        changelog.replace(
+          /^(.*)$/m,
+          `#### ${currentTag} (${currentTagDate.substr(0, 10)})`
+        ) + githubDiffLink
+      );
+    });
+  });
+
+program.parse(process.argv);

package.json

@@ -34,17 +34,21 @@
     "test:precommit": "npm test",
     "eject": "react-scripts eject",
     "lint": "npx eslint .",
+    "generate-changelog": "./bin/generate-changelog.js",
     "pretty": "npx prettier --write '**/*.{js,jsx,json,css,scss}'",
     "precommit": "lint-staged && npm run lint && npm run test:precommit",
     "serve": "npx serve --clipless --port 5000 build"
   },
   "devDependencies": {
+    "commander": "^2.15.1",
     "cross-env": "^5.1.5",
     "eslint-config-airbnb": "^16.1.0",
     "eslint-config-prettier": "^2.9.0",
     "eslint-plugin-cypress": "^2.0.1",
     "eslint-plugin-prettier": "^2.6.0",
+    "generate-changelog": "^1.7.1",
     "git-rev-sync": "^1.12.0",
+    "github-url-from-git": "^1.5.0",
     "husky": "^0.14.3",
     "lint-staged": "^7.1.2",
     "moment": "^2.22.1",