feat(tsd-test-setup): add & setup dtslint

[RobinBuschmann]

Pull Request check-list

Please make sure to review and check all of these items:

• Does npm run test or npm run test-DIALECT pass with this change (including linting)?
• Does the description below contain a link to an existing issue (Closes #[issue]) or a description of the issue you are solving?
• Have you added new tests to prevent regressions?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Did you update the typescript typings accordingly (if applicable)?
• Did you follow the commit message conventions explained in CONTRIBUTING.md?

Description of change

This PR adds and prepares dtslint in order to have better testing suite for testing typescript declarations. See #11829 for details.

solves #11829

[RobinBuschmann]

@papb Here we go. dtslint allows us to write assertions for typescript declaration files like so:

// User.ts
class User extends Model {
  name!: string;
  age!: number;
}

// some-test.ts

// $ExpectType User
User.create({name: 'Marty'});

// $ExpectError
User.create({firstName: 'Marty'});

What do you think?

If we're fine with it we also should add some hints how to use it in CONTRIBUTING.md. Do we have any rules how to handle type script typings in the contribution guidelines? Couldn't find any.

[RobinBuschmann]

Is there a way to see details for failed check continuous-integration/appveyor/pr?

[codecov]

Codecov Report

Merging #11879 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #11879   +/-   ##
=======================================
  Coverage   96.24%   96.24%           
=======================================
  Files          95       95           
  Lines        9215     9215           
=======================================
  Hits         8869     8869           
  Misses        346      346

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[sushantdhiman]

/cc @papb / @SimonSchick

[RobinBuschmann]

continuous-integration/appveyor/pr fails with:

bash : not found!
At line:4 char:3
+   bash codecov.sh -f "coverage\lcov.info"
+   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (not found!:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError

I think, there is nothing I can do to fix this?