Update downloads.html with new release

The counter is a value from github api. To see latest release you can do such thing from terminal

```
python -c "import urllib; import json; print [(x['id'], x['name']) for x in json.loads(urllib.urlopen('https://api.github.com/repos/fontforge/fontforge/releases').read())]"
```

The command will print all available releases with those ids. In https://github.com/fontforge/fontforge.github.io/edit/master/_layouts/downloads.html#L39 just replace id with new one.