[KOGITO-9839] - Add how to build a custom devmode image

[ricardozanini]

JIRA:
https://issues.redhat.com/browse/KOGITO-9839

Description:
In this PR, we add a new guide explaining how to build a custom devmode image. Please note that the idea is to expand this very same guide to final workflow images and quarkus builds too.

Please make sure that your PR meets the following requirements:

• You have read the contributions doc
• Pull Request title is properly formatted: KOGITO-XYZ Subject
• Pull Request title contains the target branch if not targeting main: [0.9.x] KOGITO-XYZ Subject
• The nav.adoc file has a link to this guide in the proper category
• The index.adoc file has a card to this guide in the proper category, with a meaningful description

How to backport a pull request to a different branch?

In order to automatically create a backporting pull request please add one or more labels having the following format backport-<branch-name>, where <branch-name> is the name of the branch where the pull request must be backported to (e.g., backport-7.67.x to backport the original PR to the 7.67.x branch).

NOTE: backporting is an action aiming to move a change (usually a commit) from a branch (usually the main one) to another one, which is generally referring to a still maintained release branch. Keeping it simple: it is about to move a specific change or a set of them from one branch to another.

Once the original pull request is successfully merged, the automated action will create one backporting pull request per each label (with the previous format) that has been added.

If something goes wrong, the author will be notified and at this point a manual backporting is needed.

NOTE: this automated backporting is triggered whenever a pull request on main branch is labeled or closed, but both conditions must be satisfied to get the new PR created.

[spolti]

why copy the requirements if it is used only on build time, it seems?

[spolti]

maybe enforce podman and Containerfile instead Dockerfile?

[ricardozanini]

I'd rather stay with Docker since it's what we have on the operator side

[spolti]

minor suggestions

[wmedvede]

LGTM.
I've added a silly suggestion that I believe can be good for people having a direct link to know how the just generated image can be used. Take a look in case it makes sense to you too.

[kaldesai]

@ricardozanini LGTM