Strong-name sign the RxSharp assembly, bump to 0.1.1

puppeteer-sharp signs its own assembly and its build fails (CS8002 under
TreatWarningsAsErrors) when referencing an unsigned dependency. Adds a
dedicated key pair and enables SignAssembly so RxSharp can be consumed
as a PackageReference from signed assemblies.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K92eapPm8e7mX7puT4cF4s

Author: kblok

keys/rxsharp.snk

@@ -16,9 +16,14 @@
     <PackageProjectUrl>https://github.com/hardkoded/ReactiveExtensions-Sharp</PackageProjectUrl>
     <RepositoryUrl>https://github.com/hardkoded/ReactiveExtensions-Sharp</RepositoryUrl>
     <PackageReadmeFile>README.md</PackageReadmeFile>
-    <PackageVersion>0.1.0</PackageVersion>
-    <AssemblyVersion>0.1.0.0</AssemblyVersion>
-    <FileVersion>0.1.0.0</FileVersion>
+    <PackageVersion>0.1.1</PackageVersion>
+    <AssemblyVersion>0.1.1.0</AssemblyVersion>
+    <FileVersion>0.1.1.0</FileVersion>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <SignAssembly>true</SignAssembly>
+    <AssemblyOriginatorKeyFile>../../keys/rxsharp.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
 
   <PropertyGroup>