add help! pseudo command

[dzharii]

Add help! modifier to the command to explain what it will do
Help can be used as dry-run mode for some command

aww create file.cs help!:
## will list all templates

aww create help
## will explain what command does

aww date help
## explains what command does

aww date i want you to help me .md help!
## will tell what the result is expected, but do not write it to clipboard