feat: export excel

Rinaldy Adinrequested to merge
feat/export-excel into dev
  • Export excel (.xls & .xlsx) to file storage
  • Send excel (.xls & .xlsx) via email app
  • Features still temporarily accessed through Floating Action Button on Transactions page
  • Use coroutines to stop UI from freezing
  • Add loading dialog when generating excel file when sending email

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