openapi-type: strictly define `ResponsesObject` type

[mirceanis]

fixes #742

This PR enables strict mode for typescript. Impressively, the project only has one issue that doesn't work in strict mode, and this PR also fixes that. You can check this quickly by running npx lerna run prepare which eventually runs tsc.

Strict mode (and this fix) is required by our project which depends directly on openapi-types, so your review of this and eventual release is much appreciated.

• [X] I only have 1 commit.
• [X] My commit is prefixed with the relevant package (e.g. express-openapi: fixing something) Note: You can use the bin/commit script to automate this.
• [X] I have added tests.
  • not explicitly a test, but npx lerna run prepare will demonstrate that the strict compilation works properly
• [X] I'm using the latest code from the master branch and there are no conflicts on my branch.
• [X] I have added a suffix to my commit message (fixes #742)
• [X] My tests pass locally.
• [X] I have run linting against my code.

[floriank]

Thank you for this PR <3

I don't wish to be pushy - but I could really use this change as this currently blocks a project of mine. Any possible ETA on the next release?

[jsdevel]

@mirceanis please update with the latest from master.

[mirceanis]

@mirceanis please update with the latest from master.

I've rebased my changes onto the latest master Please re-review

[Morl99]

We would also love to get this issue fixed. Is there anything we could do to help?

[Kosta-Github]

ping... any updates on this?