Add Accessibility info (microsoft#3717)

* Add A11y info

* Update schema 1.3 AC snapshot

Co-authored-by: William Wong <compulim@users.noreply.github.com>

Author: corinagum

README.md

@@ -226,6 +226,10 @@ Please note, however:
 -  Web Chat has no plan to support samples for IE11 (ES5).
    -  For customers who wish to manually rewrite our other samples to work in IE11, we recommend looking into converting code from ES6+ to ES5 using polyfills and transpilers like [`babel`](https://babeljs.io/docs/en/next/babel-standalone.html).
 
+## Accessibility
+
+View the [accessibility documentation](https://github.com/microsoft/BotFramework-WebChat/tree/master/docs/ACCESSIBILITY.md).
+
 ## Localization
 
 View the [localization documentation](https://github.com/microsoft/BotFramework-WebChat/tree/master/docs/LOCALIZATION.md) for implementing in Web Chat.

__tests__/.eslintrc

@@ -0,0 +1,2 @@
+globals:
+  runHTMLTest: readonly

__tests__/__image_snapshots__/html/card-action-adaptive-card-card-agenda-js-adaptive-card-card-agenda-should-fail-1-snap.png

@@ -3,5 +3,5 @@
  */
 
 describe('"Adaptive card', () => {
-  test('card agenda should fail', () => runHTMLTest('cardAction.adaptiveCard.cardAgenda.html'));
+  test('card agenda with schema 1.3 should pass', () => runHTMLTest('cardAction.adaptiveCard.cardAgenda.html'));
 });

__tests__/__image_snapshots__/html/card-action-adaptive-card-card-agenda-js-adaptive-card-card-agenda-with-schema-1-3-should-pass-1-snap.png

@@ -23,6 +23,18 @@ of new full-width/kern/smush alternatives, but default output is NOT changed.
 Font modified May 20, 2012 by patorjk to add the 0xCA0 character
 -->
 
+# Introduction
+
+We are always working to improve the accessibility of our product.
+
+You can view accessibility bugs and improvements that have already been filed using the [accessibility label](https://github.com/microsoft/BotFramework-WebChat/issues?q=is%3Aissue+is%3Aopen+label%3A%22Area%3A+Accessibility%22).
+
+The Web Chat team has a comprehensive accessibility test suite, performs thorough manual testing, and also uses [Microsoft FastPass](https://accessibilityinsights.io/docs/en/web/getstarted/fastpass/) to test new features and bug fixes.
+
+To learn more about Assistive Technologies we test and support, please view the [technical support guide](https://github.com/microsoft/BotFramework-WebChat/blob/master/docs/TECHNICAL_SUPPORT_GUIDE.md#accessibility)
+
+We welcome your feedback and will continue to improve the product in this area, as accessibility is one of our top priorities.
+
 # Focus management
 
 ## Definitions