Merge pull request #18 from openedx/update-README

Update README with out-of-date warning

README.md

@@ -1,5 +1,15 @@
 # Open edX Tech Radar
 
+## Note
+
+The Open edX Tech Radar was last updated in late 2021, and is known to be out of date.
+There is a [GitHub Issue](https://github.com/openedx/openedx-backstage/issues/27)
+around developing a process to update the Tech Radar quarterly. If you find this
+information valuable and would be able to help with a Radar update, please comment
+on that ticket.
+
+## What?
+
 The [Open edX Tech Radar Visualization](https://radar.thoughtworks.com/?sheetId=https%3A%2F%2Fopenedx.github.io%2Fopenedx-tech-radar%2Fopen-edx-primary-radar.csv) is generated by code hosted in here in [https://github.com/openedx/openedx-tech-radar](https://github.com/openedx/openedx-tech-radar). The assets used for the visualization are [published to Github Pages](https://openedx.github.io/openedx-tech-radar/) for consumption by Thoughtworks' service.
 
 ## Why?