Improve redis example

[jovekuang]

There are a few areas I think can be imporved for this redis example:

1. The example is unclear how to add a host nane as there's only a port number here

   docs/examples/scripts/redis.ts

   Line 17 in 8d5fffe

   using redisConn = await Deno.connect({ port: 6379 });

2. I am unable to get sendCommand to work by following this line.

   docs/examples/scripts/redis.ts

   Line 30 in 8d5fffe

   await redisClient.sendCommand(["SET", "hello", "world"]); // "OK"

   The error I am getting is

error: Uncaught (in promise) Error: -ERR unknown command 'SET,hello,world'
    throw new ErrorReplyError(decoder.decode(line));
          ^
    at tryParseErrorReply (https://deno.land/x/redis@v0.39.0/protocol/deno_streams/reply.ts:120:11)
    at tryReadErrorReply (https://deno.land/x/redis@v0.39.0/protocol/deno_streams/reply.ts:130:3)
    at eventLoopTick (ext:core/01_core.js:168:7)
    at async readReply (https://deno.land/x/redis@v0.39.0/protocol/deno_streams/reply.ts:24:5)
    at async RedisConnection.processCommandQueue (https://deno.land/x/redis@v0.39.0/connection.ts:366:21)

While I can get the set working by referencing the example on the Redis site here, but it's important to understand how to use sendCommand still with other Redis commands such as JSON.SET etc. I am unable to find a working example of sendCommand on the internet with JSON.SET unfortunately...