fix: add mixed to aria-checked typings (#34633)

Summary:
`aria-checked` prop should accept `mixed` as value as given [here](https://www.w3.org/WAI/GL/wiki/Using_WAI-ARIA_aria-checked%3Dmixed) and also [accessibilityState.checked](https://reactnative.dev/docs/accessibility#accessibilitystate) accepts mixed to represent checkboxes. This change refers to issue #34424 and PR #34524

## Changelog

[General] [Added] - Added `mixed` value for `aria-checked`.

Pull Request resolved: #34633

Test Plan:
```js
<TouchableOpacity
  accessibilityRole="checkbox"
  aria-checked="mixed"
  accessibilityHint="click me to change state">
  <Text>Checkbox example</Text>
</TouchableOpacity>
```

Reviewed By: lunaleaps

Differential Revision: D39382158

Pulled By: necolas

fbshipit-source-id: fa026274111305cc0bcbb42ed974ca1be7d779a5

Author: ankit-tailor

Libraries/Components/Button.js

@@ -157,7 +157,7 @@ type ButtonProps = $ReadOnly<{|
    * see https://reactnative.dev/docs/accessibility#accessibilitystate
    */
   'aria-busy'?: ?boolean,
-  'aria-checked'?: ?boolean,
+  'aria-checked'?: ?boolean | 'mixed',
   'aria-disabled'?: ?boolean,
   'aria-expanded'?: ?boolean,
   'aria-selected'?: ?boolean,

Libraries/Components/Pressable/Pressable.js

@@ -65,7 +65,7 @@ type Props = $ReadOnly<{|
    * see https://reactnative.dev/docs/accessibility#accessibilitystate
    */
   'aria-busy'?: ?boolean,
-  'aria-checked'?: ?boolean,
+  'aria-checked'?: ?boolean | 'mixed',
   'aria-disabled'?: ?boolean,
   'aria-expanded'?: ?boolean,
   'aria-selected'?: ?boolean,

Libraries/Components/Touchable/TouchableWithoutFeedback.js

@@ -54,7 +54,7 @@ type Props = $ReadOnly<{|
    * see https://reactnative.dev/docs/accessibility#accessibilitystate
    */
   'aria-busy'?: ?boolean,
-  'aria-checked'?: ?boolean,
+  'aria-checked'?: ?boolean | 'mixed',
   'aria-disabled'?: ?boolean,
   'aria-expanded'?: ?boolean,
   'aria-selected'?: ?boolean,

Libraries/Components/View/ViewAccessibility.d.ts

@@ -53,7 +53,7 @@ export interface AccessibilityProps
    * see https://reactnative.dev/docs/accessibility#accessibilitystate
    */
   'aria-busy'?: boolean | undefined;
-  'aria-checked'?: boolean | undefined;
+  'aria-checked'?: boolean | 'mixed' | undefined;
   'aria-disabled'?: boolean | undefined;
   'aria-expanded'?: boolean | undefined;
   'aria-selected'?: boolean | undefined;

Libraries/Components/View/ViewPropTypes.js

@@ -531,7 +531,7 @@ export type ViewProps = $ReadOnly<{|
    * see https://reactnative.dev/docs/accessibility#accessibilitystate
    */
   'aria-busy'?: ?boolean,
-  'aria-checked'?: ?boolean,
+  'aria-checked'?: ?boolean | 'mixed',
   'aria-disabled'?: ?boolean,
   'aria-expanded'?: ?boolean,
   'aria-selected'?: ?boolean,

Libraries/Text/TextProps.js

@@ -86,7 +86,7 @@ export type TextProps = $ReadOnly<{|
    * see https://reactnative.dev/docs/accessibility#accessibilitystate
    */
   'aria-busy'?: ?boolean,
-  'aria-checked'?: ?boolean,
+  'aria-checked'?: ?boolean | 'mixed',
   'aria-disabled'?: ?boolean,
   'aria-expanded'?: ?boolean,
   'aria-selected'?: ?boolean,