Include HTML above render root for DOM validation

[marvinhagemeister]

This fixes debug warnings when Islands are used where the preact tree is embedded into an existing HTML structure.

<table>
  <!-- preact renders here -->
</table>

Fixes denoland/fresh#1140

[coveralls]

coverage: 99.708% (+0.003%) from 99.705% when pulling 2833c8e on table-validate into ac1f145 on master.

[github-actions]

Size Change: +258 B (0%)

Total Size: 56.5 kB

Filename	Size	Change
debug/dist/debug.js	3.64 kB	+88 B (2%)
debug/dist/debug.module.js	3.62 kB	+85 B (2%)
debug/dist/debug.umd.js	3.71 kB	+85 B (2%)

ℹ️ View Unchanged

Filename	Size	Change
compat/dist/compat.js	3.92 kB	0 B
compat/dist/compat.module.js	3.84 kB	0 B
compat/dist/compat.umd.js	3.98 kB	0 B
devtools/dist/devtools.js	232 B	0 B
devtools/dist/devtools.module.js	240 B	0 B
devtools/dist/devtools.umd.js	315 B	0 B
dist/preact.js	4.26 kB	0 B
dist/preact.min.js	4.29 kB	0 B
dist/preact.min.module.js	4.29 kB	0 B
dist/preact.min.umd.js	4.32 kB	0 B
dist/preact.module.js	4.29 kB	0 B
dist/preact.umd.js	4.33 kB	0 B
hooks/dist/hooks.js	1.53 kB	0 B
hooks/dist/hooks.module.js	1.56 kB	0 B
hooks/dist/hooks.umd.js	1.62 kB	0 B
jsx-runtime/dist/jsxRuntime.js	360 B	0 B
jsx-runtime/dist/jsxRuntime.module.js	326 B	0 B
jsx-runtime/dist/jsxRuntime.umd.js	441 B	0 B
test-utils/dist/testUtils.js	442 B	0 B
test-utils/dist/testUtils.module.js	444 B	0 B
test-utils/dist/testUtils.umd.js	526 B	0 B

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