Loading WSD source code from external files.

[johnholliday]

The Docsify embed syntax does not work.

```websequencediagrams
![SequenceDiagram](_wsd/sequencediagram.wsd ':include :type=code')
```

The generated image is clipped:

The generated element is given below:

<img src="https://www.websequencediagrams.com/cgi-bin/cdraw?lz=IVt3ZWJzZXF1ZW5jZWRpYWdyYW1zXSguLi9fZ2VuZXJhdGVkL3dzZC9zdHJ1Y3R1cml6ci0xLVRheG9ub215LndzZCAnOmluY2x1ZGUgOnR5cGU9dGV4dCcp&amp;s=modern-blue">

Decoding the Base64 string yields the following:

![websequencediagrams](../_generated/wsd/structurizr-1-Taxonomy.wsd ':include :type=text')

This shows that the plugin does not recognize the docsify expression.

If the same WSD code is entered manually, the diagram is rendered properly:

The generated element is very different: