The SDCardManager.h header uses std::string in function signatures but
doesn't include the <string> header, causing build failures.
Co-authored-by: ratedcounsel <hello@ratedcounsel.com>
- Migrate over to SdFat for exFAT support
- Add new utilities:
- `openFileForWrite`
- `openFileForRead`
- `removeDir`
- Sets up a singleton and macro to access it (`SdMan`)
