update vimdoc

Author: flwyd

doc/codefmt.txt

@@ -45,6 +45,7 @@ The current list of defaults by filetype is:
   * javascript, json, html, css: js-beautify
   * javascript, html, css, markdown: prettier
   * json, jsonnet: jsonnetfmt
+  * julia: JuliaFormatter
   * kotlin: ktfmt
   * lua: luaformatterfiveone
   * nix: nixpkgs-fmt
@@ -149,6 +150,10 @@ Default: '' `
 The path to the jsonnetfmt executable.
 Default: 'jsonnetfmt' `
 
+                                             *codefmt:julia_format_executable*
+The path to the Julia formatter script, uses `bin/formatjulia.jl` bundled with
+this plugin.
+
                                               *codefmt:google_java_executable*
 The path to the google-java executable.  Generally, this should have the form:
 `java -jar /path/to/google-java`