Add browserslist file (#938)
Add browserslist file (#938)

This sets an explicit criteria for determining which browsers to support
As of today (2019-05-13), this query includes the following browsers:
and_chr 73
and_ff 66
and_qq 1.2
and_uc 11.8
android 67
android 4.4.3-4.4.4
android 4.2-4.3
baidu 7.12
chrome 73
chrome 72
chrome 71
chrome 70
chrome 69
chrome 63
chrome 61
chrome 49
edge 18
edge 17
firefox 66
firefox 65
firefox 52
ie 11
ie_mob 11
ios_saf 12.2
ios_saf 12.0-12.1
ios_saf 11.3-11.4
ios_saf 11.0-11.2
ios_saf 10.3
kaios 2.5
op_mini all
op_mob 46
opera 58
safari 12.1
safari 12
safari 11.1
safari 5.1
samsung 9.2
samsung 8.2
samsung 7.2-7.4
samsung 4
dnnsoftware/Dnn.Platform,mitchelsellers/Dnn.Platform,mitchelsellers/Dnn.Platform,mitchelsellers/Dnn.Platform,bdukes/Dnn.Platform,nvisionative/Dnn.Platform,dnnsoftware/Dnn.Platform,valadas/Dnn.Platform,dnnsoftware/Dnn.Platform,EPTamminga/Dnn.Platform,mitchelsellers/Dnn.Platform,nvisionative/Dnn.Platform,robsiera/Dnn.Platform,RichardHowells/Dnn.Platform,bdukes/Dnn.Platform,EPTamminga/Dnn.Platform,bdukes/Dnn.Platform,nvisionative/Dnn.Platform,robsiera/Dnn.Platform,dnnsoftware/Dnn.Platform,bdukes/Dnn.Platform,RichardHowells/Dnn.Platform,mitchelsellers/Dnn.Platform,RichardHowells/Dnn.Platform,EPTamminga/Dnn.Platform,valadas/Dnn.Platform,RichardHowells/Dnn.Platform,valadas/Dnn.Platform,valadas/Dnn.Platform,valadas/Dnn.Platform,robsiera/Dnn.Platform,dnnsoftware/Dnn.Platform