(fix/schematics): package.json generated scripts

[johanchouquet]

Documentation is right (https://scully.io/docs/scully-cmd-line/) for v1.0.0-beta.0, and says --project as the right way to launch those 2 scripts.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/scullyio/scully/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• [x ] Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Other... Please describe:

What is the current behavior?

When adding scully capabilities (ng add @scullyio/init) to an existing Angular project (not default project) in a Nx mono-repo, when running npm run scully, it simply fails, because it tries to launch scully --projectName=<projectName>. Same for npm run scully:serve.

Issue Number: N/A

What is the new behavior?

It works as expected.

Does this PR introduce a breaking change?

• Yes
• [ x] No

Other information

Tested on Angular 9.1.9 project on a Windows 10 machine.

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