Miscellaneous fixes and improvements

[Maronato]

Description

This PR contains lots of small and big improvements to the type system, code organization, linting, tests, etc

No changes to user-facing API have been made, though.

Related Issue

Screenshots or GIFs (if appropriate):

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)
• Linting, refactor

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.

[vercel]

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🔍 Inspect: https://vercel.com/maronato/vue-toastification/GC68s33wxupyaA6b8Qnz9kJ7HfdZ
✅ Preview: https://vue-toastification-git-misc-fixes-maronato.vercel.app

[codecov]

Codecov Report

Merging #314 (8398735) into next (f6ab972) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              next      #314   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           19        17    -2     
  Lines          530       532    +2     
  Branches       108       104    -4     
=========================================
+ Hits           530       532    +2     

Impacted Files	Coverage Δ
src/ts/composables/useDraggable.ts	100.00% <ø> (ø)
src/ts/composables/useFocusable.ts	100.00% <ø> (ø)
src/ts/composables/useHoverable.ts	100.00% <ø> (ø)
src/components/VtCloseButton.vue	100.00% <100.00%> (ø)
src/components/VtIcon.vue	100.00% <100.00%> (ø)
src/components/VtProgressBar.vue	100.00% <100.00%> (ø)
src/components/VtToast.vue	100.00% <100.00%> (ø)
src/components/VtToastContainer.vue	100.00% <100.00%> (ø)
src/components/VtTransition.vue	100.00% <100.00%> (ø)
src/index.ts	100.00% <100.00%> (ø)
... and 6 more

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