Add more examples for polar projections

[seisman]

We already have a very simple example (https://www.pygmt.org/dev/projections/nongeo/polar.html) showing how polar projection looks like, but the polar projection (-JP) is more complicated (also more powerful). We should add more examples for the polar projections.

Here are some examples from the GMT Chinese documentation.

Resources:

• Full -JP syntax
• GMT documentation
• GMT Chinese documentation

Questions:

1. Should we put it on this page https://www.pygmt.org/dev/projections/nongeo/polar.html? Or as a standalone gallery example?

[michaelgrund]

Great idea, I would put it into a standalone gallery example according to the figure you show above. Since I worked a lot with such projections in the past (and some parts were really confusing to me in the beginning) I could work on this if there are no other volunteers 😉