refactor: use `next/script` to load the Prismic Toolbar

[angeloashmore]

Types of changes

• [ ] Chore (a non-breaking change which is related to package maintenance)
• [x] Bug fix (a non-breaking change which fixes an issue)
• [ ] New feature (a non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Description

This PR changes <PrismicPreview>'s implementation to load the Prismic Toolbar from @prismicio/react's <PrismicToolbar> to Next.js's next/script.

Using next/script optimizes external script loading to work with Next.js's hydration execution. It also allows us to remove @prismicio/react as a dependency.

As of this PR, <PrismicPreview> uses next/script's lazyOnload loading strategy. This loads the Prismic Toolbar after higher priority resources have loaded, improving perceved performance. Because the toolbar is used primarily for previews and not critical data loading for public users, loading the toolbar slightly later should not be an issue.

Closes #39

Checklist:

• [ ] My change requires an update to the official documentation.
• [x] All TSDoc comments are up-to-date and new ones have been added where necessary.
• [x] All new and existing tests are passing.

🦥

[github-actions[bot]]

size-limit report 📦

Path	Size
./dist/index.cjs	5.92 KB (-33.53% 🔽)
./dist/index.js	2.75 KB (-34.9% 🔽)

[codecov-commenter]

Codecov Report

Merging #46 (433d00c) into main (bd8f2d2) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #46   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           11        11           
  Lines          713       715    +2     
  Branches        43        43           
=========================================
+ Hits           713       715    +2     

Impacted Files	Coverage Δ
src/PrismicPreview.tsx	100.00% <100.00%> (ø)

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