Bump koa-router from 13.0.1 to 13.1.1

Bumps [koa-router](https://github.com/koajs/router) from 13.0.1 to 13.1.1.
- [Release notes](https://github.com/koajs/router/releases)
- [Changelog](https://github.com/koajs/router/blob/master/HISTORY.md)
- [Commits](koajs/router@v13.0.1...v13.1.1)

---
updated-dependencies:
- dependency-name: koa-router
  dependency-version: 13.1.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -17,7 +17,7 @@
     "finished": "^1.2.2",
     "koa": "^3.0.1",
     "koa-body": "^6.0.1",
-    "koa-router": "^13.0.1"
+    "koa-router": "^13.1.1"
   },
   "devDependencies": {
     "@domenic/eslint-config": "^4.0.1",