Make public resources of extensions accessible to web container

[7118path]

Hi,
thank you very much for this docker and composer based TYPO3 setup. I have used it for testing purposes when doing extension development.
I had to add another volume to make the resources of the extension available to the web container, which means to the web client / browser.
I hope this pull request reflects this change in a correct manner and it is helpful for other working with this setup.

[t3easy]

Hi!
Thanks for feedback, nice to read someone else also use this project.

To your PR:
I don't get the need for this volume.
If I build the images for production, the hole composer project is in the web and in the php image. If there would be a volume, this volume would overlay the folder of the images and the container may runs with an outdated state of the ext folder because Docker only copies the files of the image to the volume if it's empty.

For dev environment you. Have to use both, env.dev.yml and env.dev.volumes.yml in this order to use ./ for most file and the volumes for the others.

[7118path]

Ok, I see. Maybe the need dir only arises for me, as I use your setup as a blueprint to integrate web and typo3 into my own stack of services. I do not build any image in this case, but also do not use the dev env style mounting the whole project from the host.
If this does not make sense, sorry for the PR, please just close it, and thanks again for the project, It helped me a lot!

[t3easy]

You do not have to apologize for you PR!

Maybe you can show me your use case in more detail. E.g. we could add an additional environment for that purpose.
(Since I am on vacation, I may respond delayed)

[7118path]

Well, my use case is, to have a docker based environment where I can test the composer install routine of an extension without the need to build docker images on my own. I not sure this is worth another environment. What do you think?