Check filetype for anon execution instead of file extension

The current implementation checks an anonymous buffer for the extension: 'apex'. Only in this case its possible to run the current file in an anonymous execution. 
It makes more sense to check if the filetype is 'apex' since its not necessary to save a file for anonymous execution

Author: lkalabis

lua/salesforce/execute_anon.lua

@@ -18,7 +18,7 @@ local M = {}
 M.execute_anon = function()
     Debug:log("execute_anon.lua", "Executing anonymous Apex script...")
     local path = vim.fn.expand("%:p")
-    local file_type = vim.fn.expand("%:e")
+    local file_type = vim.bo.filetype
     local default_username = OrgManager:get_default_username()
 
     if file_type ~= "apex" then