fix(formatter): void elements with slash

[ematipico]

Summary

Closes #6656

Test Plan

Added new tests

[changeset-bot]

🦋 Changeset detected

Latest commit: 4c0c3a1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch

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[codspeed-hq]

CodSpeed Performance Report

Merging #6663 will improve performances by 6.5%

_{Comparing fix/html-formatting-self-closing (4c0c3a1) with main (e581f6d)}

Summary

⚡ 1 improvements
✅ 113 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	eucjp_1600564308684076393.json[cached]	812.1 µs	762.5 µs	+6.5%