docker-galaxy-stable: libXrender.so.1: cannot open shared object file: No such file or directory

Hi @bgruening , thanks for creating this great docker image! I have a tool that uses the R Markdown package. Whenever I use the rmarkdown::render() this function in my code, it gives me this error:

/export/tool_deps/_conda/envs/mulled-v1-e42906f66f0b4446c0f35f93ca0dfe5a7ae97d6c546c525c30341daef2d11b95/bin/pandoc +RTS -K512m -RTS tool_template.utf8.md --to html --from markdown+autolink_bare_uris+ascii_identifiers+tex_math_single_backslash --output /export/galaxy-central/database/files/000/dataset_10.dat --smart --email-obfuscation none --self-contained --standalone --section-divs --template /tool_deps/_conda/envs/mulled-v1-e42906f66f0b4446c0f35f93ca0dfe5a7ae97d6c546c525c30341daef2d11b95/lib/R/library/rmarkdown/rmd/h/default.html --no-highlight --variable highlightjs=1 --variable 'theme:bootstrap' --include-in-header /tmp/Rtmp0DvuNB/rmarkdown-str5ee12aa8c2c.html --mathjax --variable 'mathjax-url:https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML' 

Output created: /export/galaxy-central/database/files/000/dataset_10.dat
Warning messages:
1: In grDevices::png(f) :
  unable to load shared object '/export/tool_deps/_conda/envs/mulled-v1-e42906f66f0b4446c0f35f93ca0dfe5a7ae97d6c546c525c30341daef2d11b95/lib/R/library/grDevices/libs//cairo.so':
  libXrender.so.1: cannot open shared object file: No such file or directory
2: In grDevices::png(f) : failed to load cairo DLL

Because of this error, all R markdown galaxy tools stop working.