add release notes to CHANGELOG.asciidoc

CHANGELOG.asciidoc

@@ -23,6 +23,27 @@ endif::[]
 [[release-notes-1.x]]
 === .NET Agent version 1.x
 
+[[release-notes-1.20.0]]
+==== 1.20.0
+
+===== Features
+- {pull}1981[#1981] Support for Azure Functions through new `Elastic.Apm.Azure.Functions` nuget package!
+- {pull}1935[#1935] Support new Elasticsearch Client: `Elastic.Clients.Elasticsearch`
+- {pull}1988[#1988] Suppport latest version of Microsoft.Data.SqlClient
+- {pull}1968[#1988] Support latest version OracleManagedDataAccess
+- {pull}1983[#1983] Loose MSVC redistributable as requirement for the profiler
+- {pull}1976[#1983] Add support for sending agent activation method to the server
+
+
+===== Bug fixes
+- {pull}1999[#1999] NullReferenceException in span compression
+- {pull}1970[#1970] Improve profiler logging by always enabling agent logging too.
+- {pull}1972[#1972] Normalize OpenTelemetry Bridge config section to `OpenTelemetryBridgeEnabled`
+- {pull}1926[#1926] Try to enable TLS 1.2 in all scenarios.
+- {pull}1964[#1964] OTel bridge span's destination service may contain null resource
+- {pull}1961[#1961] AppSettings ElasticApm:Enabled is not fully honored in ASP.NET Classic
+
+
 [[release-notes-1.19.0]]
 ==== 1.19.0