Migrate 'Videos' page

To turn the page into the default for the containing directory in the
Hugo world, the `index.html` file is renamed to `_index.html`.

Signed-off-by: Victoria Dye <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>

Author: vdye

content/videos/_index.html

@@ -0,0 +1,13 @@
+---
+section: "documentation"
+subsection: "videos"
+title: "Git - Videos"
+url: /videos.html
+aliases:
+- /videos/index.html
+---
+
+<div id='main'>
+  <h1>Videos</h1>
+  {{< videos img_suffix="@2x" dimensions="width=\"294\" height=\"164\"" >}}
+</div>