Share css across multiple sites in Firebase

I made a webgl product configurator web app. I want each app act like a small site. I want to be able to change my css at once and deploy it to all sites.

This is my firebase.json, and my css is in de public folder.

{
"hosting": [
    {
        "target": "hosting-site-1",
        "public": "public/folder-1",
        "ignore": [
            "firebase.json",
            "**/.*",
            "**/node_modules/**"
        ]
    },
    {
        "target": "hosting-site-2",
        "public": "public/folder-2",
        "ignore": [
            "firebase.json",
            "**/.*",
            "**/node_modules/**"
        ]
    }
]

}