fix: commands not found in zvm_config (#206)

When using zvm native commands in `zvm_config`, such as `zvm_cursor_style`,
you will not be able to invoke them, as they haven't be defined at the
moment `zvm_config` is invoked.

zsh-vi-mode.zsh

@@ -261,11 +261,6 @@ ZVM_REPEAT_COMMANDS=($ZVM_MODE_NORMAL i)
 # Default config function
 : ${ZVM_CONFIG_FUNC:='zvm_config'}
 
-# Load config by calling the config function
-if command -v "$ZVM_CONFIG_FUNC" >/dev/null; then
-  $ZVM_CONFIG_FUNC
-fi
-
 # Set the readkey engine (default is NEX engine)
 : ${ZVM_READKEY_ENGINE:=$ZVM_READKEY_ENGINE_DEFAULT}
 
@@ -3451,6 +3446,11 @@ function zvm_exec_commands() {
   done
 }
 
+# Load config by calling the config function
+if zvm_exist_command "$ZVM_CONFIG_FUNC"; then
+  $ZVM_CONFIG_FUNC
+fi
+
 # Initialize this plugin according to the mode
 case $ZVM_INIT_MODE in
   sourcing) zvm_init;;