Add reference to AWSSDK.SecurityToken as it's required for AssumeRoleArn option (loic-sharma#460)

Addresses loic-sharma#277 (comment)

- Adds `AWSSDK.SecurityToken` package (required for `AssumeRoleArn` option)
- Updates `AWSSDK.S3` to the latest version

Author: altso

src/BaGet.Aws/BaGet.Aws.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
@@ -8,7 +8,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="AWSSDK.S3" Version="3.3.30" />
+    <PackageReference Include="AWSSDK.S3" Version="3.3.110.20" />
+    <PackageReference Include="AWSSDK.SecurityToken" Version="3.3.104.27" />
     <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="$(MicrosoftExtensionsPackageVersion)" />
   </ItemGroup>