[DO NOT MERGE]: Added script loader

[PKulkoRaccoonGang]

Description:

Script for adding custom scripts via the Django Site configurations.

• Support global MFE_CONFIG and the MFE_CONFIG_OVERRIDES.
• Support script adding via a link via src or inside the script tag.

Example:

{
    "MFE_CONFIG_OVERRIDES": {
        "<MFE>": {
            "EXTERNAL_SCRIPTS": [
                {
                    "head": "",
                    "body": {
                        "top": "",
                        "bottom": "<script src=\"https://ai-rnd-gpu-1.itl-dev.com/widget/loader.js\"></script>"
                    }
                }
            ]
        }
    }
}

{
    "MFE_CONFIG": {
        "EXTERNAL_SCRIPTS": [
            {
                "head": "",
                "body": {
                    "top": "",
                    "bottom": "<script src=\"https://ai-rnd-gpu-1.itl-dev.com/widget/loader.js\"></script>"
                }
            }
        ]
    }
}

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