added feature to exclude commands based on user config

[dominicbraam]

1. Added function to exclude commands. It basically checks if it is in the excluded_commands list in the config file.
2. Implemented the above function within:
   • input.tsx for command prompt colour
   • commands.ts so that it would not show the command when help is run
   • shell.ts so that the command does not run
3. Added a section to exclude the commands within the config file.
4. Added a section in README.md to help users with the feature.