First timer announcement modals

[pheeria]

Problem description:

We, devs, want to notify users of any significant changes made to a website. Ideally, we want to also notify about coming i18n.

Suggested solution:

1. Create a cookie for homepage which is set only within a certain time frame for a limited time.
2. Insert some javascript which looks for a cookie on load, and if found, shows a modal.
3. To make the functionality generic, the data about the cookie, its duration and the announcement title/description, could be written and read from an .env variable as a json string. This way, we could always announce new stuff by modifying Azure config, instead of changing the codebase.

[pheeria]

@jarjan @cappyccino @starmaerker @hikes101 what do you think?