Add changesetr

.changeset/spotty-chicken-add.md

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+---
+"dom-accessibility-api": minor
+---
+
+Cache `window.getComputedStyle` results
+
+Should improve performance in environments that don't cache these results natively e.g. JSDOM.
+This increases memory usage.
+If this results in adverse effects (e.g. resource constrained browser environments), please file an issue.