Add string panel

[Ry0]

Added string panel.

[defunctzombie]

The raw message panel gets close to doing this. You can display a single field in the raw message panel so you could do /string_topic.data and it will display the value.

Does that not work as you would expect? Does this panel do something more than display the value (like support markdown?)

I'm fine adding this panel to the registry but did want to understand how we could maybe make the builtin panel better for the workflow you have in mind.

[Ry0]

@defunctzombie
Thanks for the review.
The raw message panel works fine.
The panel works well enough for debugging purposes, but I don't think it is suitable for display purposes, for example in a demo system at the exhibition.
My extension is designed to display a simple description of a robot demo system, such as “calculating trajectory for robot” or “robot is executing calculated trajectory”.

So I made it so that I can change the font type, font color, background color, etc. as well as the font size as shown below.
This allows you to simply display a description for the customer along with the robot's movements!

[defunctzombie]

Thank you for contributing a panel to help make Foxglove more useful for everyone!