- copy link button: #1396, #1168, #1668,
- synxtax highlight: #1712, #1549, #1315, #670
- z-index: #1942

Removed trailing whitespaces with

```sh
for file in `grep -r " $" * | cut -d : -f 1 | sort | uniq | grep -v " "`; do sed -i 's/[ \t]*$//' $file; done
```

and some handwork.