Fontconfig error on Ghost:6 and Ghost:6-Alpine

[PETHTH]

Getting this error, at random moments, when users are loading the site and then the docker instance crashes.
"Fontconfig error: Cannot load default config file: No such file: (null)"

Running the installs for fonts fixes it, but not sure why I am getting this error, on a new deployment.

apk add --no-cache
fontconfig
ttf-dejavu
ttf-droid
ttf-liberation
ttf-freefont

Everything is pretty standard and all works, running 5 other Ghost CMS sites, 1 using docker and 4 using CLI.
Neither of those sites have any issues, so I am bit stomped by this.

[yosifkit]

🤔 It makes sense to install fontconfig in order to provide the bits needed by sharp and hopefully prevent crashing, but I don't think we want to inflate the size of the images with font packages and would leave that up to users to install the ones they want.

[PETHTH]

I didn't bother diving into what specifcally was missing, besides fontconfig and then I installed some common fonts.
But would say, fontconfig should be included.

[tianon]

This will be easier to verify the fix in #455 if we can reproduce the issue. 🙈