Update changelog

Author: hc-github-team-tf-provider-devex

.changes/0.20.0.md

@@ -0,0 +1,11 @@
+## 0.20.0 (December 14, 2023)
+
+NOTES:
+
+* tfprotov5+tfprotov6: An upcoming release will require the FunctionServer implementation as part of ProviderServer. ([#351](https://github.com/hashicorp/terraform-plugin-go/issues/351))
+* Provider-defined function support is in technical preview and offered without compatibility promises until Terraform 1.8 is generally available. ([#351](https://github.com/hashicorp/terraform-plugin-go/issues/351))
+
+FEATURES:
+
+* tfprotov5+tfprotov6: Upgraded protocols and added types to support provider-defined functions ([#351](https://github.com/hashicorp/terraform-plugin-go/issues/351))
+

.changes/unreleased/FEATURES-20231026-164300.yaml

@@ -1,3 +1,14 @@
+## 0.20.0 (December 14, 2023)
+
+NOTES:
+
+* tfprotov5+tfprotov6: An upcoming release will require the FunctionServer implementation as part of ProviderServer. ([#351](https://github.com/hashicorp/terraform-plugin-go/issues/351))
+* Provider-defined function support is in technical preview and offered without compatibility promises until Terraform 1.8 is generally available. ([#351](https://github.com/hashicorp/terraform-plugin-go/issues/351))
+
+FEATURES:
+
+* tfprotov5+tfprotov6: Upgraded protocols and added types to support provider-defined functions ([#351](https://github.com/hashicorp/terraform-plugin-go/issues/351))
+
 ## 0.19.1 (November 15, 2023)
 
 NOTES: