add has("edge") flag for Edge

[kgibb]

Windows 10. User agent: "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.135 Safari/537.36 Edge/12.10240"

[wkeese]

Yes, of course, has("ie") returns undefined on all browsers except for IE. This is expected behavior.

Although Edge is forked from the IE code base it's technically a separate browser, with a new name. So in the same way that has("safari") returns false on Chrome, has("ie") returns false on Edge. Do you think it should be different?

We should though add a has("edge") flag.

PS: Also, like in dojo V1, need to make sure that has("chrome"), has("safari"), and has("webkit") return undefined on Edge. See dojo/dojo@ac05a45 although that change is incomplete because it forgot has("webkit").

[kgibb]

No the has("edge") flag should suffice.

[wkeese]

OK, I'll add has("edge") and make sure other flags (has("chrome"), has("safari"), has("webkit"), has("mozilla")) are false.