Update simulator.md

Fix typo 'catagorical'

Update create_application.md for MM1 parameters

change slack to discord on readme

Update nano install docs - python3-opencv vs libopencv-python

correct spelling error.

Update README.md

Just wording - Slack is deprecated, Discord server is now official communication channel.

Add missing two parameters related to RoboHat MM1.

See comments in #616

Added Hackster IO Links
Changed the link for the code.py to internal Donkey Car maintained version.

Co-authored-by: Tawn Kramer <tawnkramer@gmail.com>

joystic -> joystick

* consolidating config

* add default racer bio config to template

* multi_train changes

* Add rearlight support to mm1 circuitpython

* Add more validation on incoming calibration value

* Add stop sign detection

Co-authored-by: Jonathan Tse <jtse@proactivesystem.com.hk>

Add mobile app user guide

Make model type optional in makemovie and check model type if salient is true

2. If salient is true, check whether model type is linear or categorical. If not, exit and warn user.

Fix train script to correctly save best valuation loss model