Section height wonky in iOS when using flex elements

### Description
Section (slide) height seems to be off in iOS as if it's not accounting for the address and / or bookmarks bars. So, if something is absolutely positioned to the bottom of slide, it will be off the bottom of the screen.

### Link to isolated reproduction with no external CSS / JS
[Ideally in jsfiddle.net (https://jsfiddle.net/alvarotrigo/ea17skjr) or codepen.io (https://codepen.io/alvarotrigo/pen/NxyPPp), links to personal websites won't be reviewed unless isolated. Reported issues without a reproduction might get closed.]

https://jsfiddle.net/kirkbross/mk138yjb

### Steps to reproduce it
1. View on an iPhone (maybe Android too).
2. Notice footer text cut off when it's positioned: `absolute` in section 2 / slide1 and margin-bottom in section 3 (flex).

### This may be...
An iOS address bar thing, but I would think fullpage would have some explicit @media querries like:
```
@media all and (device-width: 768px) and (device-height: 1024px) and (orientation: landscape) {
height: 768px;
}
```

### Versions
iPad Pro / latest 13,11 iOS

### Please...
Shake your fist at the sky and curse my name if this is entirely my issue.