Add experimental tests for dealing with .env variables

tests/browser/packages/xyz/env.test.js

@@ -0,0 +1,62 @@
+describe('@aedart/xyz', () => {
+    describe('.env experiment', () => {
+
+        // This test is only able to pass if the "@import-meta-env/babel" babel plugin
+        // has been installed, and .env.example and .env files exists in the root of
+        // the project. DO NOT ENABLE THIS TEST IN CI!
+        xit('can read import.meta.env', () => {
+            // Debug
+            // console.log('ENV', import.meta.env.FOO);
+
+            const foo = import.meta.env.FOO;
+
+            expect(foo)
+                .toBe('BAR');
+        });
+
+        // @see https://import-meta-env.org/guide/getting-started/introduction.html#special-expression
+        xit('can iterate through properties in import.meta.env', () => {
+
+            console.log('import_meta_env', globalThis.import_meta_env);
+            console.log('FOO', import.meta.env.FOO);
+            console.log('Entries', Object.entries(import.meta.env));
+
+            const env = import.meta.env;
+
+            for (const property in env) {
+                console.log(`${property}: ${env[property]}`);
+            }
+        });
+
+        xit('can read and parse .env file', () => {
+
+            // globalThis.import_meta_env = JSON.parse('"import_meta_env_placeholder"');
+
+            console.log('FOO', import.meta.env.FOO);
+            console.log('import_meta_env', globalThis.import_meta_env);
+        });
+
+        // WINNER: This seems to be the most practical solution - or at least when using Webpack.
+        // Similar solutions SHOULD be available for babel, rollup, and plain typescript.
+        it('can read injected environment variables (via Webpack)', () => {
+            // Using the dotenv module and webpack, the contents if .env is injected into the _ENV
+            // variable.
+            // @see webpack.config.js
+            //console.log('ENV', _ENV);
+
+            const ENV = _ENV;
+
+            expect(ENV)
+                .withContext('_ENV has not been injected')
+                .not
+                .toBeUndefined();
+
+            expect(Reflect.has(ENV, 'FOO'))
+                .withContext('FOO does not exists in .env')
+                .toBeTrue();
+
+            expect(ENV.FOO)
+                .toBe('BAR');
+        });
+    });
+});