The add-on should tolerate slight mouse movement in long click approach

[jbhoot]

As of v3.1, the add-on ignores mouse movement entirely. However, quite often, finger may not stay steady on a touchpad during long tap. In this situation, the add-on won't respond even when the user intends to pin/unpin the tab. So, the add-on should detect marginal mouse movement and trigger the long click action.