Add survey announcement

_posts/2018-12-19-MathDB-Survey.md

+---
+layout: post
+author: kbercic
+title: "Kicking off a survey of mathematical data collections"
+tags: 
+   - Announcements
+---
+
+While there appears to be a lot of mathematical data collections 
+(in particular collections of concrete mathematical objects) out there,
+it can be hard to track them down.
+
+One of the end goals of the survey is a [website](https://mathdb.mathhub.info)
+with information on mathematical data resources, 
+the first version of which is already online.
+
+If you know of some such data, we welcome you to leave an issue on the 
+[survey wiki](https://github.com/MathHubInfo/Documentation/wiki/Math-Databases).
\ No newline at end of file