test: add comprehensive test suite (80 tests across 3 files)

Agent-Logs-Url: https://github.com/NextCommunity/NextCommunity.github.io/sessions/8c63e0cf-cc37-4897-93f8-a6195aad77f3

Co-authored-by: jbampton <418747+jbampton@users.noreply.github.com>

Author: Copilot

jest.config.js

@@ -0,0 +1,7 @@
+/** @type {import('jest').Config} */
+module.exports = {
+  testEnvironment: "node",
+  testMatch: ["**/tests/**/*.test.js"],
+  coverageDirectory: "coverage",
+  collectCoverageFrom: ["src/_data/**/*.js", ".eleventy.js"],
+};