Push down dynamic data in `/lemgram_count` response for easier typing

[arildm]

/lemgram_count returns a mapping of lemgram strings to counts. The data is on the top level of the response, beside time and ERROR.

This is a little annoying to handle in TypeScript. For other API endpoints, the following code successfully identifies an error response:

if ("ERROR" in data) {
  throw new KorpBackendError(data.ERROR.type, data.ERROR.value)
}

But when using this for /lemgram_count, this is invalid, as TypeScript believes data.ERROR could be a number (as if "ERROR" was a lemgram in a successful response).

It can easily be worked around, but I would suggest pushing the counts mapping down under a member called counts or so, to separate the dynamic data from the predictable members:

{
  "counts": {
    "katt..nn.1": 5
  },
  "time": 0.123
}