Typo: Update example to use correct command
Typo: Update example to use correct command

When creating new plugins the word 'pkg' does not exist for 'omf new' command.
The correct one is 'omf new plugin'.
wangyung/oh-my-fish,bobthecow/oh-my-fish,eugenesvk/oh-my-fish,oh-my-fish/oh-my-fish,oh-my-fish/oh-my-fish,eugenesvk/oh-my-fish,oranja/oh-my-fish,scorphus/oh-my-fish,oranja/oh-my-fish,scorphus/oh-my-fish,wangyung/oh-my-fish