Add script to plot filters

[DanicaSTFC]

This script will output the plot https://github.com/TomographicImaging/CIL/blob/master/docs/source/images/FBP_filters1.png which is currently only available in the documentation and cannot be accessed by a software using CIL.

This will be useful in the CIL-GUI and it has been discussed in https://github.com/TomographicImaging/CIL-GUI/pull/196#issuecomment-1833940042

[lauramurgatroyd]

We agreed it will output a plot of the filter that has been configured by the user - with their selected filter and cut off - not a plot of all of the options

[DanicaSTFC]

Thanks Laura, I am making a start with setting up the issue and PR with the intention of changing the details as I find out what the best way to include the plot is. I have some notes from our meetings thank you.