Accessibility: Add option to use different line styles instead of just different colours

[Jofkos]

Problem description

People that have difficulties differentiating between colours (i.e., that are "colour blind") get less utility out of this tool, as figuring out which of the lines belongs to which label can be a hassle.

The best solution to this problem, would be to use a number of different line styles (see, e.g., matplotlib's linestyles) that can always be kept apart, irrespective of the colour they are in.

Answer these questions (or I will ignore your issue)

1. Describe your platform / Operative System and the version of PlotJuggler you are using.

Irrelevant, but macOS 14.3.1, PlotJuggler 15dce41

2. Compile and try the latest version in the main branch and check if the problem persists.

I am using a version compiled from the newest commit, which is 15dce41 at the time of writing.

3. Check if the problem can be reproduced using the dummy data created by the command line argument "-t" or one of the files in the folder "datasamples".

Applies to any data file.

4. If it can't be reproduced with the dummy data, please share the CSV file or the rosbag that can be used to reproduce the problem.

Applies to any data file.