Fix style for tooltip of tasks in the plan editor

[kostobog]

Tooltip on task in the plan editor cannot be adjusted using css unless !important is used. Find and implement a better solution without !important. See 02f6744 in #168

Currently implementation can be found in src/styles/global.scss.
The css rule is:

.tippy-box {
  max-width: 1000px !important;
}

The tooltip is from package tippyjs used in react-maintenance-planner and the max-width is added as inline style in the div element.

@blcham