Fix README for group & account commands

[amit-pub]

1. While adding a group, --group is required

Readme says:

sherlock add group detective

Existing behavior:

# sherlock add group g7
❗ account name required (--name)

2. While adding an account to a group, --name is required

Readme says:

sherlock add account bakerstreet --gid detective --tag 221b

Existing behavior:

# sherlock add account  g1-a2 --gid g8 --insecure
❗ account name required (--name)

[KonstantinGasser]

@amit-pub thanks for pointing this out. Forgot to align the README when I did my last changes - thanks! 👍

[amit-pub]

@KonstantinGasser I've created the PR for the same already - #25
you can approve if its LGTY & Merge!