Add language en-us

CLOSED This issue is closed by Espertus

I propose adding support for English as spoken in the United States (en-us). Currently, there is support for en-ca and en-gb. I understand that en is assumed to be U.S. English but don't think it needs to be this way. The default English (en) used in Blockly is non-US English (using "colour"), and we find it useful to maintain a U.S. English translation (en-us) (using "color").

{{Support}

We can map it as such for your product. Here, en is assumed to be enUS.

Still action needed, or can be closed?

Nobody's complaining about "colour", so let's close it for now. Thanks.