add about docs

docs/about/contact-us.md

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+
+## Contact Us
+
+* Submit an issue
+* Email: yangxiaodong1214@126.com
+
+## CAP Team
+

docs/about/release-notes.md

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+# Release Notes
+
+---
+
+## Version 2.4.2 (2019-01-08)
+
+**Features:**
+
+* Startup the CAP with the .NET Core 2.1 BackgroundService. #265
+* Improved message delivery performance. #261
+
+**Bug Fixed:**
+
+* Fixed PostgreSql version isolation feature bug. #256
+* Fixed SQL Server sql bug for dashboard search. #266
+
+## Version 2.4.1 (2018-12-19)
+
+**Bug Fixed:**
+
+* Fixed MongoDB version isolation feature bug. (#253)