Add 2.3.0 to changelog.md & mention the breaking change in FacetFilter

[a-magdy]

We upgraded from 2.1.0 to 2.3.0 and it took us a while to understand why the requests sent from searchkit to our backend look like this:

{
 "post_filter": {
  "term": {
   "undefined": "brands"
  }
 },
 "aggs": {
  "_type3": {
   "filter": {
    "term": {
     "undefined": "brands"
    }
   },
   "aggs": {
    "undefined": {
     "terms": {}
    },
    "undefined_count": {
     "cardinality": {}
    }
   }
  }
 }
}

I had to check the commits one by one, from 2.1.0 to get the to this change: d7f9eab#diff-f172a23508b6de00b38c007df825d91a

So I think it might save someone else's time to mention the breaking change in the change log file

thanks :)

[CLAassistant]

All committers have signed the CLA.

[coveralls]

Coverage remained the same at 98.69% when pulling 8a4c129 on Quadric:update-changelog into 9cd00cd on searchkit:develop.

[zvictor]

the commit message states that there is a breaking change on it, however the notice didn't go to the changelog. it would be a good practice to always add such messages to the changelog in the same commit that causes the break.

@ssetem

[ssetem]

Thanks @zvictor , sorry it was not obvious and not in changelog