Setting default document title and meta description #555

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Feature request

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What problem does this feature solve?

Adding default <title> and <meta name="description"> based on siteConfig.title and siteConfig.description in your Saber config file.

How should this be implemented in your opinion?

Adding them to root Vue instance: https://github.com/saberland/saber/blob/a485cf80b8267ece7f25e59706a260e26130105a/packages/saber/vue-app/create-app.js#L43