[Snyk] Security upgrade koa-static from 4.0.3 to 5.0.0 (#71)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-DEBUG-3227433

samples/ts/package.json

@@ -11,7 +11,7 @@
     "https-proxy-agent": "^2.0.0",
     "koa": "^2.3.0",
     "koa-connect-history-api-fallback": "^0.3.1",
-    "koa-static": "^4.0.0",
+    "koa-static": "^5.0.0",
     "ts-node": "^9.1.1",
     "typescript": "^4.2.3"
   },