Added country flag in Color My World activity

[saurabhhere]

Fixes #920

Preview of fix:

[llaske]

Nice. That's the idea.
But I'm not a big fan of your solution to change name in all localization.
The flag is always the same whatever the current language is. Plus we cannot ask to translator to include the flag in its translation.

[saurabhhere]

We can also have the same result by creating a different js file that contains all maps with their corresponding country and then we can define them in our existing activity file to use for Tour and Colouring Mode.

Preview of js file for flags:

And then we can use flag.js like this inside existing js files:

flag[`${target_name.replace(/ /g,'_')}`]

to show the corresponding flag in Tour and Colouring Mode.

If this fix looks good to you I will push the changes

[llaske]

Sounds good.
Be careful to handle localization. The country name in your map should be the unlocalized name.

[saurabhhere]

Please have a look @llaske

[llaske]

Good job. Thanks.