Add visualizer usage example

website/docs/usage/visualizers.jade

@@ -250,6 +250,25 @@ p
 
 +h(2, "examples") Usage examples
 
++h(3, "examples-export-svg") Export SVG graphics of dependency parses
+
++code("Example").
+    import spacy
+    from spacy import displacy
+    from pathlib import Path
+
+    nlp = spacy.load('en')
+    sentences = ["This is an example.", "This is another one."]
+    for sent in sentences:
+        doc = nlp(sentence)
+        svg = displacy.render(doc, style='dep')
+        file_name = '-'.join([w.text for w in doc if not w.is_punct]) + '.svg'
+        output_path = Path('/images/' + file_name)
+        output_path.open('w', encoding='utf-8').write(svg)
+
+p
+    |  The above code will generate the dependency visualizations and them to
+    |  two files, #[code This-is-an-example.svg] and #[code This-is-another-one.svg].
 
 +h(2, "manual-usage") Rendering data manually