Add a text decoration at the end of a line and have aligned to the right of its container

[acormier]

Hi,
This is what it looks like:

But this is what it should look like:

My attempt to make it work in the playground

The example shows my attempts in both css and javascript. css would be sufficient but in javascript even better.

I also tried to do it as a content widget as described here but couldn't get that to work either. A decoration seems to be a better choice.

Any advice greatly appreciated.