Add support for loconfig.local.json

If a 'loconfig.local.json' file is present (ignored by git), its settings will be merged with those in 'loconfig.json'. Useful for customizing localhost development (see example below).

Added:
- Utility 'config.js' to prepare build settings.
- Function 'merge()' for recursively merging objects and concatenating arrays.

Example:

```json
{
    "paths": {
        "url": "yourlocal.dev"
    },
    "server": {
        "open": true,
        "https": {
            "key": "~/.config/valet/Certificates/{% paths.url %}.key",
            "cert": "~/.config/valet/Certificates/{% paths.url %}.crt"
        }
    }
}
```

build/tasks/styles.js

@@ -1,4 +1,4 @@
-import loconfig from '../../loconfig.json';
+import loconfig from '../utils/config.js';
 import message from '../utils/message.js';
 import notification from '../utils/notification.js';
 import postcss, { pluginsMap as postcssPluginsMap } from '../utils/postcss.js';