Add position position fixed mode

[stalkerg]

Currently, the tooltip puts alongside the original element, and if, for example, the container has overflow: hidden it's broken.
The tooltip shouldn't rely on the original element container.

[stalkerg]

or position absolute from root element how https://atomiks.github.io/tippyjs/ is work

[stalkerg]

also, very important to determine what input element should be immutable - https://github.com/svelte-plugins/tooltips/blob/main/src/action.js#L35 this is not working in many, many cases.

[dysfunc]

I planned to release a new tooltip version that provides absolute/fixed positioning. I just need to the time to work on it, which I currently don't. PR's are always welcome though :)