docs: Make custom index page; add more docs.

docs/conf.py

docs/contents.rst

docs/hardware/index.rst

docs/index.rst

docs/library/index.rst

docs/library/pyb.SPI.rst

docs/library/struct.rst

docs/license.rst

docs/topindex.html

docs/tutorial/amp_skin.rst

docs/tutorial/index.rst

docs/tutorial/lcd_skin.rst

docs/tutorial/repl.rst

docs/tutorial/script.rst