fix: point type exports to correct file

[guidojw]

Description

Since release 6.4.0, types aren't exported correctly anymore, it looks like the dts directory doesn't exist anymore (related to the gulp removal I think?). This PR points the package.json types to lib/index.d.ts. It also exports the results classes under a namespace "results", as was done in 6.3.2 too and broken by the ESLint PR.

Related Issue

inversify/InversifyJS#1387

Motivation and Context

Projects will correctly find the types again, and results imports will work again.
I have 0 experience with multi-platform type exports and stuff, so please do tell if I messed something up.

How Has This Been Tested?

My TypeScript 4.4.3 project is able to find the types again and the results imports are working again.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

(it breaks a breaking change (the results export), so I guess that's a breaking change?)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[guidojw]

@dcavanagh Hi! Types work on version 6.4.2 pulled from npm but the results export fix doesn't seem to be included there yet.