Provide browser support information

[kalnode]

It's known that some browsers (e.g. IE11) don't fully support flexbox and/or support an earlier specification of flexbox.

While playing this game, it would be nice to know, at any point, what the browser support is for each flexbox feature. If there's a particular feature that needs a workaround, or performs differently, it would be nice to know.

Conversely... if all of these basic flexbox features are fully supported, even in IE11, then at least there should be a message indicating that too!

thx

[WatsonFungHK]

sounds good