How to add flowchart.js to hugo?

Hello, I'm using hugo for my blog. I add
```javascript

```
to `themes/paperback/layouts/partials/footer.html`. And create new post `flowchart.md`:
```flow
st=>start: Start
e=>end: End
op1=>operation: Caculate

st->op1->e
```
But those codes are rendered as code, not rendered as flowchart at all. Any suggestion?