fix(vega): add v4 mime type (#821)

* fix(vega): add v4 mime type

The v4 mime type is what is currently supported out of the box by Jupyter, v3 requires an extension to be installed

* style(vegaMime): use list comprehensions

src/display.jl

@@ -35,7 +35,8 @@ This is necessary to embed the JSON as is in the displaydata bundle (rather than
 as stringify'd JSON).
 """
 const ijulia_jsonmime_types = Vector{Union{MIME, Vector{MIME}}}([
-    [MIME("application/vnd.vegalite.v2+json"), MIME("application/vnd.vega.v3+json")],
+    [[MIME("application/vnd.vegalite.v$n+json") for n in 3:-1:2]...,
+    [MIME("application/vnd.vega.v$n+json") for n in 5:-1:3]...],
     MIME("application/vnd.dataresource+json"), MIME("application/vnd.plotly.v1+json")
 ])
 
@@ -164,4 +165,4 @@ function error_content(e, bt=catch_backtrace();
                  "traceback" => tb)
 end
 
-#######################################################################
+#######################################################################

src/inline.jl

@@ -6,8 +6,8 @@ struct InlineDisplay <: AbstractDisplay end
 # of preference (descending "richness")
 const ipy_mime = [
     "application/vnd.dataresource+json",
-    "application/vnd.vegalite.v2+json",
-    "application/vnd.vega.v3+json",
+    ["application/vnd.vegalite.v$n+json" for n in 3:-1:2]...,
+    ["application/vnd.vega.v$n+json" for n in 5:-1:3]...,
     "application/vnd.plotly.v1+json",
     "text/html",
     "text/latex",