This fixes security issue
[CVE-2023-42282](https://github.com/advisories/GHSA-78xj-cgh5-2h22),
which is not very likely to be exploitable in MagicMirror² setups, but
still should be fixed.
The [express-ipfilter](https://www.npmjs.com/package/express-ipfilter)
package depends on the obviously unmaintained
[ip](https://github.com/indutny/node-ip) package, which has known
security vulnerabilities. Since no fix is available, this commit
replaces both dependencies with a custom middleware using the better
maintained [ipaddr.js](https://www.npmjs.com/package/ipaddr.js) library.
Changes:
- Add new `js/ip_access_control.js` with lightweight middleware
- Remove `express-ipfilter` dependency, add `ipaddr.js`
- Update `js/server.js` to use new middleware
- In addition, I have formulated the descriptions of the corresponding
tests a little more clearly.
