Release 0.2.0: changelog, version reporting, push-to-deploy

- CHANGELOG.md following Keep a Changelog, covering 0.1.0 and 0.2.0
- server/version.js reads the version from package.json; /healthz returns it
  and the footer renders it, so a deployment always states what it is serving
- bump package.json 0.1.0 -> 0.2.0

server/routes.js

@@ -1,6 +1,7 @@
 import QRCode from 'qrcode';
 import { Router, HttpError, readBody, send, esc } from './http.js';
 import { publicState } from './public-state.js';
+import { VERSION } from './version.js';
 import * as pub from './views/public.js';
 import * as adm from './views/admin.js';
 
@@ -12,7 +13,7 @@ export function buildRouter({ registry, auth, store }) {
 
   // ---------- public ----------
   r.get('/', (req, res) => send.html(res, pub.homePage(registry.list())));
-  r.get('/healthz', (req, res) => send.json(res, { ok: true, tournaments: registry.items.size, uptime: process.uptime() }));
+  r.get('/healthz', (req, res) => send.json(res, { ok: true, version: VERSION, tournaments: registry.items.size, uptime: process.uptime() }));
 
   r.get('/t/:slug', (req, res, { slug }) => {
     const it = item(slug);