nand-backup: sync with finalizing-setup @ 8c2613d88b

This brings the NAND backup steps up to speed with the more up-to-date
Finalizing Setup prior to adding an automated script, which fixes
a few issues such as:
- missing step to copy `.bin.sha` from the SD card
- inconsistency where guide tells to copy `essential.exefs` without
  extracting it first

_pages/en_US/include/nand-backup.txt

@@ -10,10 +10,16 @@
 1. Press (B) to return to the main menu
 1. Select "Exit"
 1. Press (A) to relock write permissions if prompted
+1. Navigate to `[S:] SYSNAND VIRTUAL`
+1. Press (A) on `essential.exefs` to select it
+1. Select "Copy to 0:/gm9/out"
+    + If you see "Destination already exists", press (A) on "Overwrite file(s)"
+1. Press (A) to continue
 1. Hold (R) and press (Start) at the same time to power off your console
 1. Insert your SD card into your computer
-1. Copy `<date>_<serialnumber>_sysnand_##.bin` and `essential.exefs` from the `/gm9/out/` folder on your SD card to a safe location on your computer
-    + Make backups in multiple locations (such as online file storage)
+1. Copy `<date>_<serialnumber>_sysnand_##.bin`, `<date>_<serialnumber>_sysnand_##.bin.sha`, and `essential.exefs` from the `/gm9/out/` folder on your SD card to a safe location on your computer
+    + Copy these backups to multiple locations (such as online file storage, an external hard drive, etc.)
     + These backups will save you from a brick and/or help you recover files from the NAND image if anything goes wrong in the future
 1. Delete `<date>_<serialnumber>_sysnand_##.bin` and `<date>_<serialnumber>_sysnand_##.bin.sha` from the `/gm9/out/` folder on your SD card after copying it
+    + The other backup files are negligible in size and may be kept on your SD card for ease of access
 1. Reinsert your SD card into your console