Update Dockerfile

Add enumitem, which is a plugin that allows editing the nesting of things. See https://stackoverflow.com/questions/57945414/too-deeply-nested-at-just-fourth-nesting-level-using-pandoc-with-markdown

Author: chrisfenner

Dockerfile

@@ -33,7 +33,8 @@ RUN tlmgr update --self && \
     ulem \
     hardwrap \
     catchfile \
-    ragged2e
+    ragged2e \
+    enumitem
 
 RUN apk upgrade && apk add --no-cache \
     bash \