Validate as a standalone command or earlier in process

This is a Feature Proposal

Description

For feature proposals:

• Currently, it appears that the step function definition validation only occurs when executing sls package. This is a long executing step, and it would be easier if we could have a way to validate the step function without going through sls package.
• Recently, while writing a step function definition, I misspelled the key word "Resource" within a task definition. Although I had the validate flag set to true, the sls package command exited before it got to validate because the misspelling caused issues with the IAM role creation. This led to a long period of debugging to discover that the cause was a misspelled word, when, in theory, the validate step would have caught the problem well ahead of that stage and described the problem to us, thus saving us a lot of time.
• Barring a standalone command for validate, moving the validate check to the start of the sequence of sls package steps would be equally useful. The earlier we can get a more human readable version of potential definition errors, the better.

Additional Data

• Serverless Framework Core Version you're using: 1.46.1
• The Plugin Version you're using: 2.7.0
• Operating System: Mac OS

Start by tracing the validation flow triggered by the validate flag during sls package, including the point where IAM role creation can fail first. Define whether completion means adding a standalone validation command or moving validation earlier in sls package, then verify that misspelled Step Functions definitions produce a readable error before the longer packaging steps.