docs: re-write interpolation section and add example (#25170)

PR Close #25170

aio/content/examples/interpolation/e2e/src/app.e2e-spec.ts

@@ -0,0 +1,47 @@
+import { browser, element, by } from 'protractor';
+
+describe('Interpolation e2e tests', () => {
+
+  beforeEach(function () {
+    browser.get('');
+  });
+
+  it('should display Interpolation and Template Expressions', function () {
+    expect(element(by.css('h1')).getText()).toEqual('Interpolation and Template Expressions');
+  });
+
+  it('should display Current customer: Maria', function () {
+    expect(element.all(by.css('h3')).get(0).getText()).toBe(`Current customer: Maria`);
+  });
+
+  it('should display The sum of 1 + 1 is not 4.', function () {
+    expect(element.all(by.css('p:last-child')).get(0).getText()).toBe(`The sum of 1 + 1 is not 4.`);
+  });
+
+  it('should display Expression Context', function () {
+    expect(element.all(by.css('h2')).get(1).getText()).toBe(`Expression Context`);
+  });
+
+  it('should display a list of customers', function () {
+    expect(element.all(by.css('li')).get(0).getText()).toBe(`Maria`);
+  });
+
+  it('should display two pictures', function() {
+    let pottedPlant = element.all(by.css('img')).get(0);
+    let lamp = element.all(by.css('img')).get(1);
+
+    expect(pottedPlant.getAttribute('src')).toContain('pottedPlant');
+    expect(pottedPlant.isDisplayed()).toBe(true);
+
+    expect(lamp.getAttribute('src')).toContain('lamp');
+    expect(lamp.isDisplayed()).toBe(true);
+  });
+
+  it('should support user input', function () {
+    let input = element(by.css('input'));
+    let label = element(by.css('label'));
+    expect(label.getText()).toEqual('Type something:');
+    input.sendKeys('abc');
+    expect(label.getText()).toEqual('Type something: abc');
+  });
+});