Expand generate.py section in readme.
Expand generate.py section in readme.

quentinyang/pannellum,eric-seekas/pannellum,eric-seekas/pannellum,riuson/pannellum,riuson/pannellum,ywjrg/pannellum,mpetroff/pannellum,mpetroff/pannellum,psteph801/psteph801.github.io,psteph801/psteph801.github.io,Benvii/pannellum,quentinyang/pannellum,mpetroff/pannellum,riuson/pannellum,mpetroff/pannellum,psteph801/psteph801.github.io,quentinyang/pannellum,psteph801/psteph801.github.io,ywjrg/pannellum,ywjrg/pannellum,quentinyang/pannellum,Benvii/pannellum,eric-seekas/pannellum,riuson/pannellum,eric-seekas/pannellum,Benvii/pannellum,Benvii/pannellum,ywjrg/pannellum