[Feature] support config poptip trigger event

[xuefei1313]

What problem does this feature solve?

in mobile text poptip-plugin only trigger by TouchMove, should support trigger by TouchDown event

What does the proposed API look like?

poptip: { trigger: 'pointerover' | 'pointerdown' }

[xuefei1313]

移动端poptip的触发逻辑不好用，通过配置trigger支持pointerdown下触发