docs: Add Playstation information to README (shaka-project#4322)

README.md

@@ -39,6 +39,8 @@ For details on what's coming next, see our [development roadmap](roadmap.md).
 |Tizen TV³  | -        | -       | -       | -       | -        | -      |**Y**|
 |WebOS⁶     | -        | -       | -       | -       | -        | -      |**Y**|
 |Xbox One   | -        | -       | -       | -       | -        | -      |**Y**|
+|Playstation 4⁷| -        | -       | -       | -       | -        | -      |**Y**|
+|Playstation 5⁷| -        | -       | -       | -       | -        | -      |**Y**|
 
 NOTES:
  - ¹: On macOS, only Safari 13+ is supported.  On iOS, only iOS 13+ is
@@ -53,6 +55,8 @@ NOTES:
    us.
      - Official support for LG WebOS TV:
        https://github.com/shaka-project/shaka-player/issues/1330
+ - ⁷: These are expected to work, but are community-supported and untested by
+   us.
 
 We support iOS 13+ through Apple's native HLS player.  We provide the same
 top-level API, but we just set the video's `src` element to the manifest/media.
@@ -149,6 +153,8 @@ HLS features **not** supported:
 |Tizen TV  |**Y**     |**Y**    | -       |untested⁵ |
 |WebOS⁷    |untested⁷ |untested⁷| -       |untested⁷ |
 |Xbox One  | -        |**Y**    | -       | -        |
+|Playstation 4⁷| -        |untested⁷| -       |untested⁷ |
+|Playstation 5⁷| -        |untested⁷| -       |untested⁷ |
 
 Other DRM systems should work out of the box if they are interoperable and
 compliant to the EME spec.