fix(deps): update dependency luxon to v3.3.0 & add @types/luxon (#689)

## Description
- added `@types/luxon` to dependencies
- updated Luxon from `v3.2.1` to `v3.3.0` (avoided `v3.4.0` since types
aren't available for that version yet).

## Related Issue
Fixes #688.

## Motivation and Context
This library needs to depend on `@types/luxon` since we now export our
own types. See the related issue for the error this fixes.

## How Has This Been Tested?
- checked that TypeScript now correctly loads the Luxon types
- ran tests locally

## Types of changes
- [X] 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)

## Checklist:
- [X] 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 added tests to cover my changes.
- [X] All new and existing tests passed.
- [ ] If my change introduces a breaking change, I have added a `!`
after the type/scope in the title (see the Conventional Commits
standard).

package.json

@@ -20,7 +20,8 @@
 	},
 	"types": "types/index.d.ts",
 	"dependencies": {
-		"luxon": "^3.2.1"
+		"@types/luxon": "~3.3.0",
+		"luxon": "~3.3.0"
 	},
 	"devDependencies": {
 		"@commitlint/cli": "~17.6.6",