added description in detail for trackClicks (#182)
added description in detail for trackClicks (#182)

* added description in detail for trackClicks

* nits

* Update description

Co-authored-by: Tung Vu <2fccf87c1c89af65e3a6bd16938ea785fce05062@users.noreply.github.com>

Co-authored-by: dnson <2d0040ef8f0a963b879cb18b7ea36fc1f44b58d7@treasure-data.com>
Co-authored-by: Tung Vu <2fccf87c1c89af65e3a6bd16938ea785fce05062@users.noreply.github.com>
treasure-data/td-js-sdk,treasure-data/td-js-sdk