add item param

Changed the text rendering mode in the picker component,
From:
using innerText rendering with <li>{{...}}</li>
To:
using innerHTML rendering with <li v-html="..."></li>

This does not change anything for text items, but allows to insert HTML templates, especially icons.

All the tests seem to be ok.

* feat(index-list): add "options" props

* docs(index-list): update document about props "options"

* refactor: deprecated

* [update] scroll pulldown logic

* [update] scroll example

* [update] get pulldown ele height by js

* [update] remove unused code

* [fix]

* updated scroll.vue by review suggest

* update scroll examples

* [update] scroll docs, add introduction for stopTime

* delete earlier scroll example

* [update]{scroll.md} update English document about stopTime and stop

* [update] via review suggest

* [udpate]{example} fix style and replace v-if to v-show

* [udpate] replace promise to callback, and
replace nextTick.then to nextTick, and
repalce class text to cube-pulldown-loaded

#221