adding shortcuts on the video player buttons controltext

[barisgul15]

Motivation and Context

fixes #1289

Description

• [x] shortcuts are added to video players buttons. before: play -> after play (k)]
• [x] keyboard shortcuts should be added to the menu under keyboard icon

Steps for Testing

1. Log in
2. Navigate to a Video
3. Check the text appears when the mouse is on one of the player buttons
4. Open menu at the home page and click keyboard icon

Screenshots

It used to say only play, not the keyboard shortcuts are also displayed. Keyboard shortcuts in menu: Keyboard shortcuts popup: