Merge pull request #308 from cmu-delphi/sgratzl/release_notes_v2.3

add release notes for v2.2.0 and v2.3.0

Author: sgratzl

content/covidcast/release-log/headless/v2.2.0.md

@@ -0,0 +1,10 @@
+---
+title: v2.2.0
+date: 2021-04-01
+---
+
+### New Features
+ * Indicator Status Overview dashboard: Explore the status of API indicators and their coverages
+
+
+More information: https://github.com/cmu-delphi/www-covidcast/releases/tag/v2.2.0

content/covidcast/release-log/headless/v2.3.0.md

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+---
+title: v2.3.0
+date: 2021-04-15
+---
+
+### New Features
+ * Explore Correlations: Explore correlations between different indicators
+ * Annotation Overview: Show all data anomalies recorded in COVIDcast in a central place
+ * Expandable Line Charts: Expand the line chart of indicators to show the full historic range
+ * HHS and Nation Support: The classic map now supports displaying HHS region and national level data
+
+
+More information: https://github.com/cmu-delphi/www-covidcast/releases/tag/v2.3.0