Add images/ for webserver and indexserver used in the chart

These will initially push to the container registry for this project but will likely in future be pushed to another image repository that isn't GitLab.com for reliable access even if Gitlab.com is down.

How to test it

1. docker build -t zoekt-dynamic-indexserver -f images/Dockerfile.zoekt-dynamic-indexserver .
2. docker build -t zoekt-webserver -f images/Dockerfile.zoekt-webserver .
3. mkdir /tmp/zoekt-repos /tmp/zoekt-index && sudo chown 100:100 /tmp/zoekt-*
4. docker run -p 6060:6060 --name zoekt-dynamic-indexserver --rm -v /tmp/zoekt-repos:/data/repos -v /tmp/zoekt-index:/data/index zoekt-dynamic-indexserver
5. docker run -p 6070:6070 --name zoekt-webserver --rm -v /tmp/zoekt-index:/data/index zoekt-webserver
6. curl -XPOST -d '{"CloneUrl":"https://gitlab.com/gitlab-org/gitlab-elasticsearch-indexer.git","RepoId":2953390}' -H 'Content-Type: application/json' http://127.0.0.1:6060/index
7. See search results

   $ curl -XPOST -d '{"Q":"gitaly","RepoIDs":[2953390]}' 'http://127.0.0.1:6070/api/search' |jq .
   
    {
      "Result": {
        "ContentBytesLoaded": 58728,
        "IndexBytesLoaded": 441,
        "Crashes": 0,
        "Duration": 464177,
        "FileCount": 11,
        "ShardFilesConsidered": 0,
        "FilesConsidered": 11,
        "FilesLoaded": 11,
        "FilesSkipped": 0,
        "ShardsScanned": 1,
        "ShardsSkipped": 0,
        "ShardsSkippedFilter": 0,
        "MatchCount": 96,
        "NgramMatches": 116,
        "Wait": 18076,
        "RegexpsConsidered": 0,
        "FlushReason": 0,
        "Files": [
          {
            "Score": 727.3157894736842,
            "Debug": "",
            "FileName": "git/gitaly.go",
            "Repository": "2953390",
   ...