Merge pull request #986 from jgmdev/PR/doc-upper-lower-utf8

Add utf8 support on doc lower and upper commands

data/core/commands/doc.lua

@@ -402,11 +402,11 @@ local commands = {
   end,
 
   ["doc:upper-case"] = function()
-    doc():replace(string.upper)
+    doc():replace(string.uupper)
   end,
 
   ["doc:lower-case"] = function()
-    doc():replace(string.lower)
+    doc():replace(string.ulower)
   end,
 
   ["doc:go-to-line"] = function()