Added Blazor projects. Minor API/core updates.

JSMR.UI.Blazor/wwwroot/service-worker.js

@@ -0,0 +1,4 @@
+// In development, always fetch from the network and do not enable offline support.
+// This is because caching would make development more difficult (changes would not
+// be reflected on the first load after each change).
+self.addEventListener('fetch', () => { });