Inserted newlines in code block selections due to "user-select: none"

A strange behaviuor when I copy & paste the code block from the web page:

rendered text:
```
$ BASE=ppp-multi-image
$ DEV=sdb # i.e. sdb or mmcblk0
$ ATTR=RequiredPartition,LegacyBIOSBootable
$ SIZE=11GiB
```

copied & pasted text:
```
BASE=ppp-multi-image

DEV=sdb # i.e. sdb or mmcblk0

ATTR=RequiredPartition,LegacyBIOSBootable

SIZE=11GiB
```

Every line add a new-line.