docs(input): add overview examples for input (#5228)

src/material-examples/input-errors/input-errors-example.ts

@@ -0,0 +1,17 @@
+import {Component} from '@angular/core';
+import {FormControl, Validators} from '@angular/forms';
+
+const EMAIL_REGEX = /^[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$/;
+
+@Component({
+  selector: 'input-errors-example',
+  templateUrl: 'input-errors-example.html',
+  styleUrls: ['input-errors-example.css'],
+})
+export class InputErrorsExample {
+
+  emailFormControl = new FormControl('', [
+    Validators.required,
+    Validators.pattern(EMAIL_REGEX)]);
+
+}