add StopSplitter example

[raybellwaves]

notebook diff renders aren't great. Can add https://www.reviewnb.com/ to the repo here to help with this.

Otherwise, take a look at source (https://github.com/raybellwaves/movingpandas-examples/blob/SpeedSplitter-ex/1-tutorials/6-splitting-trajectories.ipynb) and you can run the binder to test if you like (https://mybinder.org/v2/gh/anitagraser/movingpandas-examples/main?filepath=1-tutorials/6-splitting-trajectories.ipynb).

I added a sentence between each splitter. Happy to have feedback there. I've added them below as well:

• ObservationGapSplitter: Split the trajectory where then are no observations for at least two minutes
• StopSplitter: Split the trajectory where observation stay within 30 CRS units for at least 1 minute. Discard created trajectories that are shorter than 500 CRS units long
• SpeedSplitter: Split the trajectory where the speed is below one CRS unit for at least five minutes

[anitagraser]

Thank you for this contribution, Ray!

trajectories that are shorter than 500 CRS units long

It's a little more complicated, as described in the documentation: "Length is calculated using CRS units, except if the CRS is geographic (e.g. EPSG:4326 WGS84) then length is calculated in metres."

[raybellwaves]

Given the example is in EPSG:4326 i'll use meters. Thanks