chore(dockerfile): use alpine images to reduce the size of Docker images

[wivwiv]

PR Checklist

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What is the current behavior?

Please describe the current behavior and link to a relevant issue.

Issue Number

Example: #123

What is the new behavior?

Please describe the new behavior or provide screenshots.

Use the alpine image, a lighter base image to build the MQTTX CLI Docker, and be able to reduce the size by 600MB.

In the future we could consider putting the pkg compiled binary package into an alpine image that does not contain the nodejs runtime.
The image would then be only 60MB in size.
The reason for not implementing this now is that it requires a more complex build step

Does this PR introduce a breaking change?

• Yes
• No

Specific Instructions

Are there any specific instructions or things that should be known prior to review?

Other information

[github-actions]

with the code patch review:

1. The first line changes the base image from "node:16" to "node:16-alpine". This is a good change as it will reduce the size of the container image and help the application run faster.

2. The second line sets the working directory to "/app", which is a good practice.

3. The third line copies all the files from the current folder to the "/app" directory. This is also a good practice, as it ensures that all the necessary files are available for the application.

Overall, the code patch looks good and should work as expected.