doc: add information about building production image

[tcoch]

Due to issues #745 (probably) and #751 (and some seens on StackOverflow also), I propose to be a little more precise about the building of production images.

[7-zete-7]

Hi, @tcoch!

Thank you for adding this information to the manual. This is really important information!

It seems to me that it is better not to place the instructions on how the project should be built for deployment in the Deployment section.

Perhaps it would be worth adding an additional section like Preparing for deployment?

Then, in addition to clarifying the command for building the image, it would be possible to list some nuances when working with images of this template.

[tcoch]

Hi @7-zete-7,
I kinda like the production.md file as it is, I don't want it to have too much informations.
I'm thinking maybe I could add these extra informations to the troubleshooting.md file ? WDYT ?

[7-zete-7]

Sounds very reasonable, @tcoch!

You are right, it will be better than my suggestion. And the production.md file will not be overloaded with information.

[maxhelias]

Thanks for this contribution, I just have one question

[maxhelias]

Thanks @tcoch !