[docs] Improve code block detection for RN docs importer #3356
Description
See #3337 which fixes a one-off issue with the docs that are imported from RN. The "in code block?" detection in the importer script has some edge cases, leading to issues like the one that was linked. Potentially relevant code from the importer:
expo/docs/scripts/import-react-native-docs.js
Lines 149 to 153 in ef8b2cf