Add unit testing support with vitest (#18)

* update loose files and add vitest

* update test scripts

* more support for vitest

* more test support

* update vscode settings

.vscode/settings.json

@@ -0,0 +1,4 @@
+{
+  "javascript.preferences.importModuleSpecifierEnding": "minimal",
+  "typescript.preferences.importModuleSpecifierEnding": "minimal"
+}