EuiFormHelpText converted to TS (#1852)

* `EuiFormHelpText` converted to TS

* `EuiFormHelpText` updated Changelog

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - Use `cache-loader` to speed up development docs site build ([#1841](https://github.com/elastic/eui/pull/1841)
 - Converted `matching_options` to TS ([#1828](https://github.com/elastic/eui/pull/1828))
+- Converted `EuiFormHelpText` to TS ([#1852](https://github.com/elastic/eui/pull/1852))
 
 **Bug fixes**
 

src/components/form/form_help_text/form_help_text.test.js → src/components/form/form_help_text/form_help_text.test.tsx

@@ -1,18 +1,15 @@
 import React from 'react';
 import { render } from 'enzyme';
-import { requiredProps } from '../../../test/required_props';
+import { requiredProps } from '../../../test';
 
 import { EuiFormHelpText } from './form_help_text';
 
 describe('EuiFormHelpText', () => {
   test('is rendered', () => {
     const component = render(
-      <EuiFormHelpText {...requiredProps}>
-        This is help text.
-      </EuiFormHelpText>
+      <EuiFormHelpText {...requiredProps}>This is help text.</EuiFormHelpText>
     );
 
-    expect(component)
-      .toMatchSnapshot();
+    expect(component).toMatchSnapshot();
   });
 });

src/components/form/form_help_text/form_help_text.tsx

@@ -0,0 +1,16 @@
+import React, { FunctionComponent, HTMLAttributes } from 'react';
+
+import classNames from 'classnames';
+import { CommonProps } from '../../common';
+
+export const EuiFormHelpText: FunctionComponent<
+  CommonProps & HTMLAttributes<HTMLDivElement>
+> = ({ children, className, ...rest }) => {
+  const classes = classNames('euiFormHelpText', className);
+
+  return (
+    <div className={classes} {...rest}>
+      {children}
+    </div>
+  );
+};

src/components/form/form_help_text/index.ts

@@ -0,0 +1 @@
+export { EuiFormHelpText } from './form_help_text';