Add links to Jsonnet user Tweets and blog posts on the website

Some potential user reviews to include on the website / in a tweetstream:

* https://twitter.com/brett_viren/status/1012799324932268032
* https://wirecell.github.io/news/posts/pgrapher-configuration-improvements/ (linked from above Tweet)
* https://twitter.com/rxin/status/1012031650279182344
* https://qiita.com/yugui/items/f4a5e0e9dbd8ddffa48e (in Japanese)

and, of course, these well-known blog posts:

* [Databricks blog post](https://databricks.com/blog/2017/06/26/declarative-infrastructure-jsonnet-templating-language.html)
* [Bitnami blog post](https://engineering.bitnami.com/articles/an-example-of-real-kubernetes-bitnami.html)

Some others for consideration:

* [Jsonnet used for Apache Aurora configuration](https://github.com/benley/aurora-jsonnet)
* [HN thread on Jsonnet](https://news.ycombinator.com/item?id=17363871)