fix(installer): don't overwrite previous config (#3154)

utils/installer/install.sh

@@ -439,7 +439,8 @@ function setup_lvim() {
 
   setup_shim
 
-  cp "$LUNARVIM_BASE_DIR/utils/installer/config.example.lua" "$LUNARVIM_CONFIG_DIR/config.lua"
+  [ ! -f "$LUNARVIM_CONFIG_DIR/config.lua" ] \
+    && cp "$LUNARVIM_BASE_DIR/utils/installer/config.example.lua" "$LUNARVIM_CONFIG_DIR/config.lua"
 
   echo "Preparing Packer setup"