docs/conf.py: Include 3 levels of ToC in latexpdf output.
docs/conf.py: Include 3 levels of ToC in latexpdf output.

Instead of default 2. 3 are required to access description of individual
library modules.

bvernoux/micropython,tralamazza/micropython,oopy/micropython,kerneltask/micropython,AriZuu/micropython,lowRISC/micropython,AriZuu/micropython,tralamazza/micropython,pozetroninc/micropython,Timmenem/micropython,MrSurly/micropython,micropython/micropython-esp32,AriZuu/micropython,pozetroninc/micropython,tobbad/micropython,infinnovation/micropython,adafruit/micropython,torwag/micropython,micropython/micropython-esp32,SHA2017-badge/micropython-esp32,blazewicz/micropython,swegener/micropython,dmazzella/micropython,dmazzella/micropython,tobbad/micropython,pramasoul/micropython,kerneltask/micropython,pfalcon/micropython,alex-robbins/micropython,MrSurly/micropython-esp32,chrisdearman/micropython,adafruit/circuitpython,TDAbboud/micropython,infinnovation/micropython,infinnovation/micropython,trezor/micropython,selste/micropython,henriknelson/micropython,infinnovation/micropython,deshipu/micropython,selste/micropython,alex-robbins/micropython,PappaPeppar/micropython,ryannathans/micropython,HenrikSolver/micropython,HenrikSolver/micropython,kerneltask/micropython,dmazzella/micropython,tobbad/micropython,chrisdearman/micropython,pramasoul/micropython,kerneltask/micropython,pramasoul/micropython,SHA2017-badge/micropython-esp32,ryannathans/micropython,selste/micropython,micropython/micropython-esp32,MrSurly/micropython,tralamazza/micropython,adafruit/micropython,MrSurly/micropython-esp32,blazewicz/micropython,HenrikSolver/micropython,TDAbboud/micropython,MrSurly/micropython-esp32,trezor/micropython,oopy/micropython,AriZuu/micropython,oopy/micropython,swegener/micropython,deshipu/micropython,selste/micropython,MrSurly/micropython,pfalcon/micropython,deshipu/micropython,lowRISC/micropython,swegener/micropython,lowRISC/micropython,bvernoux/micropython,HenrikSolver/micropython,alex-robbins/micropython,swegener/micropython,tobbad/micropython,henriknelson/micropython,adafruit/micropython,Timmenem/micropython,micropython/micropython-esp32,adafruit/micropython,torwag/micropython,alex-robbins/micropython,pozetroninc/micropython,adafruit/circuitpython,MrSurly/micropython-esp32,TDAbboud/micropython,infinnovation/micropython,alex-robbins/micropython,AriZuu/micropython,henriknelson/micropython,pfalcon/micropython,adafruit/micropython,pfalcon/micropython,chrisdearman/micropython,Timmenem/micropython,MrSurly/micropython-esp32,MrSurly/micropython,oopy/micropython,TDAbboud/micropython,chrisdearman/micropython,PappaPeppar/micropython,Timmenem/micropython,micropython/micropython-esp32,dmazzella/micropython,SHA2017-badge/micropython-esp32,HenrikSolver/micropython,bvernoux/micropython,torwag/micropython,oopy/micropython,Timmenem/micropython,PappaPeppar/micropython,deshipu/micropython,adafruit/circuitpython,chrisdearman/micropython,swegener/micropython,lowRISC/micropython,tobbad/micropython,bvernoux/micropython,pozetroninc/micropython,blazewicz/micropython,blazewicz/micropython,blazewicz/micropython,tralamazza/micropython,MrSurly/micropython,torwag/micropython,henriknelson/micropython,adafruit/circuitpython,trezor/micropython,bvernoux/micropython,adafruit/circuitpython,PappaPeppar/micropython,SHA2017-badge/micropython-esp32,ryannathans/micropython,torwag/micropython,pramasoul/micropython,kerneltask/micropython,pramasoul/micropython,PappaPeppar/micropython,pfalcon/micropython,ryannathans/micropython,trezor/micropython,lowRISC/micropython,ryannathans/micropython,selste/micropython,SHA2017-badge/micropython-esp32,pozetroninc/micropython,adafruit/circuitpython,trezor/micropython,TDAbboud/micropython,henriknelson/micropython,deshipu/micropython