Add GDC(Gradient denscent coregistration) in documentation

[liuh886]

Planning to add a GDC section in co-registration, including

• a clear example of using GDC
• a clear limitation
• usage suggestions: point-raster-coregistration, subsampling, weight

This is a follow-up of #346. Welcome any suggestions you may have.

[rhugonnet]

Definitely something to do, thanks for adding this issue @liuh886!
We were planning on "refurbishing" the Coreg documentation pages after adding plotting and stats functionalities mentioned in #435 (to not have to do it twice!), normally sometime within the next month.

[rhugonnet]

But if you have something in mind and time now, we can also update existing pages and examples after adding the plotting/stats functionalities 😉

[liuh886]

Definitely something to do, thanks for adding this issue @liuh886!
We were planning on "refurbishing" the Coreg documentation pages after adding plotting and stats functionalities mentioned in #435 (to not have to do it twice!), normally sometime within the next month.

wow, I will put my eyes on #435, and address this issue in the following document refurbishing.😊