Update apps.json

Modified "CMS Made Simple" apps rule by adding "headers" for CMSSESSID cookie detection suggestion by @gadcam
You have to keep the first pattern you tried because I think this one is a bit too broad as <code>SSESSID</code> is a very common name of cookie and CMS is also a generic term, some false positives will occur.
You have to escape the <code>\\</code> (see https://github.com/ElbertF/Wappalyzer/wiki/Specification, a very useful page if you want to contribute) so you should write :
```js
"headers": { "Set-Cookie": "^CMSSESSID[\\da-f]{8}$" }
```