Refactor mobile chat into modal (#3038)

* feat(mobile): refactor mobile chat into modal

- Make page always scrollable
- Move mobile chat into a standalone modal

* fix(test): split out mobile browser test specs

* fix(mobile): force chat button to render on top of footer

* fix: some small updates from review

* fix: hide/show hide chat menu option based on width

* fix: chat button icon getting cut off

* chore(tests): add browser tests for mobile chat modal

* chore(tests): add story for ChatModal component

* fix(test): quiet shellcheck

* fix: remove unused import

* fix(tests): silence storybook linting warning

* fix(ui): reposition chat modal button icon with transform

web/components/common/UserDropdown/UserDropdown.module.scss

@@ -3,20 +3,31 @@
 .root {
   button {
     border: none;
-		.ant-space {
-			.ant-space-item {
-				color: var(--theme-unknown-2);
-			}
-		}
+    .ant-space {
+      .ant-space-item {
+        color: var(--theme-unknown-2);
+      }
+    }
   }
 
-	.username {
-	  display: none;
+  .username {
+    display: inline;
 
-	  @include screen(desktop) {
-		  display: inline;
-			font-weight: 600;
-			font-size: .8rem;
-	  }
+    @include screen(desktop) {
+      font-weight: 600;
+      font-size: 0.8rem;
+    }
+  }
+
+  .hideTitleOnMobile {
+    @include screen(mobile) {
+      display: none;
+    }
+  }
+}
+
+.chatToggle {
+  @include screen(mobile) {
+    display: none;
   }
 }