breaking change : re-implement custom mappings | simplify it | add whichkey

fixes #1057 , #1047

lua/core/default_config.lua

@@ -31,10 +31,6 @@ M.plugins = {
    remove = {},
 
    options = {
-      packer = {
-         init_file = "plugins.packerInit",
-         snapshot = nil,
-      },
       lspconfig = {
          setup_lspconf = "", -- path of lspconfig file
       },
@@ -50,9 +46,7 @@ M.plugins = {
    user = {},
 }
 
--- non plugin only
-M.mappings = {
-   misc = function() end,
-}
+-- check core.mappings for table structure
+M.mappings = require "core.mappings"
 
 return M