Javascript References in Code Blocks are Expanded

[kihashi]

OS

Windows 10
Backslide@feature/refactor

Problem

When using export, script references in a code block are expanded:

```html
<script src="index.js"></script>
```

Results in this:

<script src=\"file://C:\\Users\\John\\Documents\\presentation\\slides/index.js\"><\/script>

Expected Result

HTML inside code blocks is not changed

Observed Result

File reference inside a code block was changed to use an absolute path

Related Issue: #29