add imagemagick-svg *back* to all the alpine images

[jessebot]

(Context: Alpine changed their imagemagick packaging)

This is an alternative to #2220 to move it forward. Followed the instructions per this comment: #2220 (review)

I can do another PR for imagemagick-pdf as well if you want, but to keep this short and simple, I've only done svg here, as that's the only one that throws a warning.

[joshtrichards]

I can do another PR for imagemagick-pdf as well if you want, but to keep this short and simple, I've only done svg here, as that's the only one that throws a warning.

👍 Thank! Let's get this in since it's the most pressing with 29.0.3 right around the immediate corner.

But let's also create an issue now (or, better yet, WIP PR) to propose & firm up what others should also be added back in, in a follow-up[1].

[1] We probably want to keep parity. Is there anything that doesn't belong or should we just load all of them back in to mirror the old packaging?

Cc: @felix-egli

[jessebot]

@joshtrichards unless I misunderstood, I think this is what we wanted to do next for adding pdf support:
#2248

[jessebot]

@J0WI and/or @joshtrichards is there anything we can do to ensure this gets into the next release?

[jessebot]

Thanks for getting this over the line! I know this is a community maintained docker repo and everyone is doing their best! 💙