Add function to show current year in the intro text

[maeriens]

This is to show the current year, addressing issue #68

I have literally no idea how I managed it, I simply copied more or less how the data was being replaced in the 2nd slide. I guess that's what people call programming.

[nerdius]

A better approach would be using a <span> with an unique ID, then selecting that from JavaScript and assigning a value to its innerHTML. There's also no need to have a function at all.

Here's the code:

HTML:

Meanwhile: it's <span id="current-year"></span>, the West has been at peace for decades, and

JavaScript:

document.querySelector('#current-year').innerHTML = new Date().getFullYear();