feat: add covidcast v1.12.3 changelog

Author: sgratzl

content/covidcast/release-log/headless/v1.12.3.md

@@ -0,0 +1,17 @@
+---
+title: v1.12.3
+date: 2021-01-12
+---
+
+#### Signal Changes
+
+- Add "Vaccine Acceptance" signal to map and survey dashboard
+
+#### New Features
+
+- [#709](https://github.com/cmu-delphi/www-covidcast/pull/709), [#710](https://github.com/cmu-delphi/www-covidcast/pull/710), [#708](https://github.com/cmu-delphi/www-covidcast/pull/708) Improve loading performance especially for the survey dashboard
+- [#712](https://github.com/cmu-delphi/www-covidcast/pull/712) Improve map style
+
+#### Bug-fixes
+
+- [#713](https://github.com/cmu-delphi/www-covidcast/pull/713) fix trend color for decreasing trends