Vue 3, define global mixin in TS in VSCode (with Volar)

Hello,
I use Typescript for the first time and I have a small issue.

I defined two global methods in mixin in main.ts:

// ...

interface toast {
    title_cs: string,
    title_en: string,
    type: "success" | "danger" | "warning"
}

app.mixin({
    methods: {
        pushToast(toast: toast): void {
            this.$store.dispatch("toast/pushToast", toast);
        },
        removeToast(id: number): void {
            this.$store.dispatch("toast/removeToast", id);
        }
    }
})

// ...

How to define those ‘global methods’ (probably in types.d.ts - but dunno how) so the typescript/volar/vscode knows it’s global and stop highlight it as an error inside components?

Thanks for help.