fix windows config setup

[UziTech]

When initially setting up the new config file in windows we need to escape any backslashes in the folder path

before:

{
    "uris": [
        "file://C:\folder"
    ],
    "indexDatabaseUri": "file://C:\Users\user\AppData\Roaming\php-ide-serenata\index-5c51a4ab6ab1bda8bf0d2e20c0bdc99f.sqlite",
    "phpVersion": 7.3,
    "excludedPathExpressions": [],
    "fileExtensions": [
        "php"
    ]
}

after:

{
    "uris": [
        "file://C:\\folder"
    ],
    "indexDatabaseUri": "file://C:\\Users\\user\\AppData\\Roaming\\php-ide-serenata\\index-5c51a4ab6ab1bda8bf0d2e20c0bdc99f.sqlite",
    "phpVersion": 7.3,
    "excludedPathExpressions": [],
    "fileExtensions": [
        "php"
    ]
}

[Gert-dev]

Thanks for taking the time to fix issues with this package on Windows. LGTM!