Fix expand/collapse tree button of Data Explorer page is not accessible through keyboard (#1067)

* Fix ally issues for newCollection panel's advanced section

* Resolved test snapshot issue

* Fix a11y data explorer expand/collapse using keyboard issue

src/Common/ResourceTreeContainer.tsx

@@ -1,4 +1,4 @@
-import React, { FunctionComponent } from "react";
+import React, { FunctionComponent, MutableRefObject, useEffect, useRef } from "react";
 import arrowLeftImg from "../../images/imgarrowlefticon.svg";
 import refreshImg from "../../images/refresh-cosmos.svg";
 import { AuthType } from "../AuthType";
@@ -6,6 +6,7 @@ import Explorer from "../Explorer/Explorer";
 import { ResourceTokenTree } from "../Explorer/Tree/ResourceTokenTree";
 import { ResourceTree } from "../Explorer/Tree/ResourceTree";
 import { userContext } from "../UserContext";
+import { NormalizedEventKey } from "./Constants";
 
 export interface ResourceTreeContainerProps {
   toggleLeftPaneExpanded: () => void;
@@ -18,6 +19,22 @@ export const ResourceTreeContainer: FunctionComponent<ResourceTreeContainerProps
   isLeftPaneExpanded,
   container,
 }: ResourceTreeContainerProps): JSX.Element => {
+  const focusButton = useRef<HTMLLIElement>() as MutableRefObject<HTMLLIElement>;
+
+  useEffect(() => {
+    if (isLeftPaneExpanded) {
+      if (focusButton.current) {
+        focusButton.current.focus();
+      }
+    }
+  });
+
+  const onKeyPressToggleLeftPaneExpanded = (event: React.KeyboardEvent) => {
+    if (event.key === NormalizedEventKey.Space || event.key === NormalizedEventKey.Enter) {
+      toggleLeftPaneExpanded();
+      event.stopPropagation();
+    }
+  };
   return (
     <div id="main" className={isLeftPaneExpanded ? "main" : "hiddenMain"}>
       {/* Collections Window - - Start */}
@@ -43,9 +60,11 @@ export const ResourceTreeContainer: FunctionComponent<ResourceTreeContainerProps
                 id="expandToggleLeftPaneButton"
                 role="button"
                 onClick={toggleLeftPaneExpanded}
+                onKeyPress={onKeyPressToggleLeftPaneExpanded}
                 tabIndex={0}
                 aria-label="Collapse Tree"
                 title="Collapse Tree"
+                ref={focusButton}
               >
                 <img className="refreshcol1" src={arrowLeftImg} alt="Hide" />
               </span>