Add 10.6.21 release notes

Author: MariaShaposhnikova

content/en/docs/releasenotes/studio-pro/10/10.6.md

@@ -10,7 +10,16 @@ mts: true
 This is the [MTS](/releasenotes/studio-pro/lts-mts/#mts) version 10 release for apps in production.
 {{% /alert %}}
 
-## 10.6.20
+## 10.6.21 {#10621}
+
+**Release date: February ___, 2024**
+
+{{% button color="info" href="https://marketplace.mendix.com/link/studiopro/10.6.21" text="Go to Marketplace" title="Download version 10.6.21 from the Marketplace" %}}
+### Fixes
+
+* We added a setting to enable Windows Authentication for a private Git server. (Ticket 234161)
+
+## 10.6.20 {#10620}
 
 **Release date: February 4, 2024**
 
@@ -31,7 +40,7 @@ This is the [MTS](/releasenotes/studio-pro/lts-mts/#mts) version 10 release for
 * We fixed an error where apps became stuck during unstable internet connections.
 * We fixed a bug where disposed tool windows were still considered active in the UI, causing Studio Pro to crash when the active editor changed.
 
-## 10.6.19
+## 10.6.19 {#10619}
 
 **Release date: January 8, 2024**