support timeseries multiple labels with same key

[luasenvy]

Description

purpose:
support timeseries array labels

problem:
currently client.ts.create() is allow LABELS options for only { [key: string]: string }.
so, cannot use multiple label with same key like:

TS.CREATE MyKey labels hashtag=helloworld hashtag=ineed hashtag=multiple hashtag=labels

solve:
this PR is allow Array<string> too.

const LABELS = {
  hashtag: ['helloworld', 'ineed', 'multiple', 'labels'],
  someother: 'mykey'
}
await client.ts.create('MyKey', { LABELS })

I couldn't find any related issues. sorry for my search availity.

I think this feature will help make the code better.

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Checklist

• Does npm test pass with this change (including linting)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?