Disable validation of output smithy files by default.

[Baccata]

This makes the tool a little bit more lenient for some users. A flag is added to re-enable validation.

also changes the CLI options to be kebab-cased

Todo

• [x] Fix modules that don't compile
• [x] Add unit tests to check that validation of output can be re-enabled.
• [x] Amend README to expose new options