ABC notation library is outdated

### Is this a hackmd.io issue?

- [x] Yes, the bug happens on https://hackmd.io
- [ ] No. If it's a self-hosted CodiMD instance, please fire up the issue in the repo of CodiMD: https://github.com/hackmdio/codimd

### What's the problem

#### Current behaviour

Try rendering the following small example as abc notation:

```abc
T:Minimal example showing the bug
K:C
CD EF
w:line* one
w:line two
```

Word _two_ appears on the top line, while it should belong to the bottom line; see rendering here: https://hackmd.io/tCiCmcSiQ-qzcTyHNY6LJQ

#### Expected behaviour

There should be blank between words _line_ and _one_ on the top line (indicated with star), and word _two_ should be at the bottom line.

#### Additional information

This seems to be a bug in the old version of the `abcjs` library used by hackmd, currently. To see the correct rendering you can copy and paste the same content to a test editor which uses the latest version of `abcjs`: https://editor.drawthedots.com/