Create thick-islands-share.md

Author: JoviDeCroock

.changeset/thick-islands-share.md

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+---
+"preact-render-to-string": patch
+---
+
+Improve performance by
+
+- storing the void_elements in a Set
+- hoisting the `x-link` regex
+- remove case-insensitive from regexes and calling `.toLowerCase()` instead
+- caching suffixes for css-props