Release NodaTime.Serialization.SystemTextJson version 1.3.0

Changes since 1.2.0:

- Support `Nullable<T>` properties with source generation
- Fixed link in package readme
- Updated System.Text.Json dependency to 8.0.5

Author: jskeet

src/NodaTime.Serialization.SystemTextJson/NodaTime.Serialization.SystemTextJson.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <Description>Provides serialization support between Noda Time and System.Text.Json</Description>
     <!-- Update this just before a release. -->
-    <Version>1.2.0</Version>
+    <Version>1.3.0</Version>
     <!-- Update this just after a release. -->
     <PackageValidationBaselineVersion>1.2.0</PackageValidationBaselineVersion>