Add a different color to the options that are commands when shown on the gh help

Signed-off-by: Henrique Vicente <henriquevicente@gmail.com>
Add feature to only list a command options if gh help cmd was used to avoid cluttering the screen and add info about the git help cmd command

Signed-off-by: Henrique Vicente <henriquevicente@gmail.com>
Add gh help --all cmd to list all the options of all commands

Signed-off-by: Henrique Vicente <henriquevicente@gmail.com>
Add info about the gh help --all on the README and more

Signed-off-by: Henrique Vicente <henriquevicente@gmail.com>
Instead if adding a different color to the options that are commands when shown on the gh help just add a suffix "-f, --flag*"
Always show help footer
Improve help readme