[bugfix] Utils: <is-src> data URLs should be prefixed with the data:i…

…mage (youzan#3308)

[improvement] check event.cancelable before preventDefault

[bugfix] Step: incorrect active step when insert step asynchronously

Merge branch 'dev'

[release] 1.6.15

[bugfix] Step: step 销毁之前从父 steps 中移除 (youzan#3140)

[Doc] Stepper: optimize async demo (youzan#3098)

[bugfix] Picker: render error when set data async (youzan#3064)

[new feature] Sku: set selectedNum when inited (youzan#3045)

[new feature] Icon: add tag prop (youzan#2986)