Add accessibility labels

[mikemee]

Let's improve accessibility as suggested by Google Play as follows:

id/guide_toolbar/AppComatImageButton[0] "Close"

id/mal_list_card - various

I don't think the cards add much value here given that the labels are clearly defined.

Per https://support.google.com/accessibility/android/answer/7158690, let's explicitly mark each of these cards as not requiring content:

Decorative images or images that don't convey meaningful information graphically do not require content labels. In these cases, set an android:contentDescription attribute of "@null" or an android:importantForAccessibility attribute of "no".