Support for KEYS Command

Problem Statement

Missing 'KEYS' command. https://redis.io/commands/KEYS

If the proposed solution looks good I can create propper MR with documentation and code

Proposed Solution

Something like this would be nice to have

extension RedisClient {
    public func keys(_ key: RedisKey) -> EventLoopFuture<[RedisKey]> {
        let args = [RESPValue(from: key)]
        return self.send(command: "KEYS", with: args)
    }
}