feat(): add optional --strict flag on "nest new"

[micalevisk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• 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?

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

What is the current behavior?

Issue Number: nestjs/schematics#597

What is the new behavior?

CLI users can use nest new --strict if they want to turn on TypeScript's strict mode in their projects from beginning, ie. the following TS compiler options will be true instead of the default false: strictNullChecks, noImplicitAny, strictBindCallApply, forceConsistentCasingInFileNames and noFallthroughCasesInSwitch

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

I upgraded @nestjs/schematics dependency to 8.0.3 to use the strict option of it.
I changed the semver range in package.json to make this requirement explicit.

[kamilmysliwiec]

LGTM