Install mmdc, to allow the rendering of mermaid diagrams

[phertweck]

In the current version the rendering of Mermaid diagrams is not working

Failed to generate image: Could not find the 'mmdc' executable in PATH; add it to the PATH or specify its location using the 'mmdc' document attribute

In this Pull request the mmdc is installed in the docker image.

[rdmueller]

thanx for this contribution. Sorry, that this took me so long to check.

Two suggestions:

• the docker image is already quite heavy. Shouldn't we create a new docker image to that people can chose?
• we can add all diagram libraries one by one, but there is also kroki.io already available. Wouldn't it be a great approach if we add the kroiki-server?

[pdelrot-samea]

Hello. I use a Synology NAS for gitlab and kroki (for the gitlab wiki which supports kroki), both as dockers.
I've just added a docToolchain docker image as I intends to use docToolChain for gitlab Pages.

A separate kroki server/docker will be fine for me.
Pascal

[phertweck]

I agree that adding mmdc increases the image size. I'd also prefer the kroki solution, since mmdc has some strange errors with some of my test diagrams.

Is there an easy solution to configure a kroki server in docToolchain?

[ehmkah]

I am not sure whether this is a good solution. But i created an other docker-image which has doctoolchain + pandoc. At least it was accepted. :-D

Maybe you you just copy this approach and create the new image with kroki in it. Example can be found in the PR #38 if you have questions just ask.

[rdmueller]

I wonder how many images we should maintain.
My main goal was to have one small image. I missed this goal by at least 1GB :-)

The pandoc image is not much bigger than the standard image. Should we merge both?

what about mmdc? How much will it add? Would it make sense to add a kroki server instead to support all diagram types?