chore(travis): set cron event

scripts/generate.ts

@@ -0,0 +1,11 @@
+import * as fs from 'fs';
+import {create_cheat_sheet} from '../src/create-cheat-sheet';
+
+const output_filename = process.argv[2];
+if (output_filename === undefined) {
+  throw new Error(`Usage ts-node path/to/generate.ts path/to/output.md`);
+}
+
+create_cheat_sheet().then(cheat_sheet => {
+  fs.writeFileSync(output_filename, cheat_sheet, 'utf8');
+});