Initialize unit testing and code coverage

* add: vitest configs

* added vitest scripts to package

* test coverage of src code

* initial unit testing

* added new testing workflows

* comments added, overlapping tests removed

* decouple env, tests

---------

Co-authored-by: Kevin Dang <kevinthedang_1@outlook.com>

vitest.config.ts

@@ -0,0 +1,12 @@
+import { defineConfig, configDefaults } from 'vitest/config'
+
+// config for vitest
+export default defineConfig({
+    test: {
+        globals: true, // <-- reduces test file imports
+        coverage: {
+            exclude: [...configDefaults.exclude, 'build/*'], // <-- exclude JS build
+            reporter: ['text', 'html'] // <-- reports in text, html
+        }
+    }
+})