BREAKING CHANGE: May not be compatible with 4.x.
Since default symbol animation with line charts has been changed in 5.0 to be
displayed when the clipPath of the line goes through the data point,
animationDelay callback now has two meanings:
animationDelay: function (i) { return ... }
(1) If `i` is `null`, the callback should return the delay of the overall
    series animation, that is, the delay before the line clipPath starts
    changing.
(2) If `i` is a `number`, the callback should return the delay of the certain
    delay of each data item.
In ECharts 4.x, however, since the label animation shows along with the line
animation, only the `number` form is used.

Fix: make `contentToOption` totally optional

fix(tooltip): keep axis tooltip open on refresh

Fix lint problem in next

fix: [data-transform] (1) update the sort rule for string and incomparable value. update test cases. (2) `parser: 'number'` supports suffix parse (like '100%', '20px').

Dataset trans2

fix(bar-race): fix bug with animation

fix(model/Global): fix a typo.

seiresIndex -> seriesIndex

fix: [data-transform] Make the comparison operation accurate in common edge cases. Support parser 'number'.