style(lint): update spellcheck glob for new .mdx files so check applies

Author: mikehardy

package.json

@@ -19,7 +19,7 @@
     "lint:ios:fix": "find packages/*/ios -type f \\( -name '*.h' -o -name '*.cpp' -o -name '*.m' -o -name '*.mm' \\) -not -path '*/generated/*' -print0 | xargs -0 clang-format -i --style=Google",
     "lint:markdown": "eslint \"docs/**/*.mdx\" --max-warnings=0 && prettier --check \"docs/**/*.mdx\"",
     "lint:report": "eslint --output-file=eslint-report.json --format=json . --ext .js,.jsx,.ts,.tsx",
-    "lint:spellcheck": "spellchecker --quiet --files=\"docs/**/*.md\" --dictionaries=\"./.spellcheck.dict.txt\" --reports=\"spelling.json\" --plugins spell indefinite-article repeated-words syntax-mentions syntax-urls frontmatter",
+    "lint:spellcheck": "spellchecker --quiet --files=\"docs/**/*.{md,mdx}\" --dictionaries=\"./.spellcheck.dict.txt\" --reports=\"spelling.json\" --plugins spell indefinite-article repeated-words syntax-mentions syntax-urls frontmatter",
     "tsc:compile": "tsc --project .",
     "tsc:compile:consumer": "tsc --project tsconfig.consumer.json",
     "lint:all": "yarn lint && yarn lint:markdown && yarn lint:spellcheck && yarn tsc:compile",