Enable scale item column in rqt sub-window

[jacknlliu]

Every rqt plugin like topic monitor, we can't scale the item column width, this lead that we can't see every detail easily.

[dirk-thomas]

Each rqt plugin is providing the UI on its own. Therefore rqt can't do anything about it. Please consider filling issues in the issue tracker of each plugin which has this problem (e.g. https://github.com/ros-visualization/rqt_topic). It will likely speed up the fix if you could provide a pull request for these plugins.

Since there is nothing which can be done in this repository I will close the ticket. Please feel free to comment and e.g. add references to other tickets you are creating for future readers.