docs(tutorial/0 - Bootstrapping): describe your change...

[tbwork]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  NO
• What is the current behavior? (You can also link to an open issue here)
• What is the new behavior (if this is a feature change)?
• Does this PR introduce a breaking change?

NO

• Please check if the PR fulfills these requirements
• The commit message follows our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Other information:

As describe below "The ng-app attribute represents an Angular directive named ngApp (Angular uses
spinal-case for its custom attributes and camelCase for the corresponding directives
which implement them).". ng-app is an attribute, not a directive.

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[googlebot]

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[gkalpak]

Closed with c2033d7.