[Diagram Editor] Config example browser

[mxgrey]

#115 introduces both a help text description of a node builder and a list of config examples with explanations of each example, however the PR only exposes the help text description to the front end, leaving the config examples hidden.

We should follow up with some UI element that allows users to browse and select example configs. This should probably come after #105 since that one is more crucial for UX.