Added the mathquestion command

[FreemRL]

Added new command /mathquestion

• [x] Code is formatted correctly
• [X] Code is tested before submitting
• [X] Updated README.md commands list with my new command

Details

I added the /mathquestion command refering to #16.

Features:

Optional command options:

min --> The minimum number a user wants to play with. max --> The maximum number a user wants to play with. mode --> easy: 30 seconds to answer, medium: 20 seconds to answer, hard: 10 seconds to answer.

By default the min. number will be 20 and the max. number will be 400. Also the mode will be easy (30 seconds to reply).

Some Example Images:

[details]

[FreemRL]

By the way I had to make small changes in index.js to get this to work :)