cloud: deck screenshot emoji support

[peterpeterparker]

Affected part of DeckDeckGo

• Cloud

Reproduction

When a deck is published, a screeshot of the first slide is taken in the cloud in order to create the social image card.

Currently, this process doesn't seems to support emoji.

For example, the social card of the following deck doesn't render such emoji:

Deck: https://beta.deckdeckgo.io/daviddalbusco/1000-sign-ups/
Social card: https://twitter.com/daviddalbusco/status/1257690415714705408

[peterpeterparker]

This is the related issue of Puppeeteer in Firebase: puppeteer/puppeteer#4086