release: Bump runtime to 0.4.0 (#340)

## Breaking Changes

* extism/extism#315

HTTP calls will be disallowed by default now. If you want to enable HTTP
you need to specify the hosts that the plug-in is allowed to communicate
with. If you want to allow all hosts you can set it to `{allowed_hosts:
["*"]}` in the manifest. However, this isn't recommended unless you have
some trust in the plug-in or are controlling the networking by some
other means.

* extism/extism#335

In this PR we are creating an implicit context so people don't need to
know about it if they don't care. In some languages function signatures
have changed to make context an optional argument when creating a
plug-in.

dotnet/nuget/Extism.runtime.win.csproj

@@ -8,7 +8,7 @@
 
     <PropertyGroup>
         <PackageId>Extism.runtime.win-x64</PackageId>
-        <Version>0.5.0</Version>
+        <Version>0.6.0</Version>
         <Authors>Extism Contributors</Authors>
         <Description>Internal implementation package for Extism to work on Windows x64</Description>
         <Tags>extism, wasm, plugin</Tags>