Update all mkdir commands to create parent directories if necessary

Author: zeorin

README.md

@@ -635,7 +635,7 @@ sudo mkfs.ext2 /dev/mapper/gnupg-secrets -L gnupg-$(date +%F)
 Mount the filesystem and copy the temporary GnuPG working directory with key materials:
 
 ```console
-sudo mkdir /mnt/encrypted-storage
+sudo mkdir -p /mnt/encrypted-storage
 
 sudo mount /dev/mapper/gnupg-secrets /mnt/encrypted-storage
 
@@ -717,7 +717,7 @@ $ doas newfs sd3i
 Mount the filesystem and copy the temporary directory with the keyring:
 
 ```console
-doas mkdir /mnt/encrypted-storage
+doas mkdir -p /mnt/encrypted-storage
 
 doas mount /dev/sd3i /mnt/encrypted-storage
 
@@ -760,7 +760,7 @@ Create a filesystem and export the public key:
 ```console
 sudo mkfs.ext2 /dev/sdc2
 
-sudo mkdir /mnt/public
+sudo mkdir -p /mnt/public
 
 sudo mount /dev/sdc2 /mnt/public
 
@@ -794,7 +794,7 @@ Create a filesystem and export the public key to it:
 ```console
 doas newfs sd2b
 
-doas mkdir /mnt/public
+doas mkdir -p /mnt/public
 
 doas mount /dev/sd2b /mnt/public
 
@@ -1052,15 +1052,15 @@ Mount the non-encrypted volume with the public key:
 **Debian/Ubuntu**
 
 ```console
-sudo mkdir /mnt/public
+sudo mkdir -p /mnt/public
 
 sudo mount /dev/sdc2 /mnt/public
 ```
 
 **OpenBSD**
 
 ```console
-doas mkdir /mnt/public
+doas mkdir -p /mnt/public
 
 doas mount /dev/sd3i /mnt/public
 ```
@@ -1938,15 +1938,15 @@ Decrypt and mount the encrypted volume:
 ```console
 sudo cryptsetup luksOpen /dev/sdc1 gnupg-secrets
 
-sudo mkdir /mnt/encrypted-storage
+sudo mkdir -p /mnt/encrypted-storage
 
 sudo mount /dev/mapper/gnupg-secrets /mnt/encrypted-storage
 ```
 
 Mount the non-encrypted public partition:
 
 ```console
-sudo mkdir /mnt/public
+sudo mkdir -p /mnt/public
 
 sudo mount /dev/sdc2 /mnt/public
 ```
@@ -2045,7 +2045,7 @@ sudo cryptsetup luksClose gnupg-secrets
 Export the updated public key:
 
 ```console
-sudo mkdir /mnt/public
+sudo mkdir -p /mnt/public
 
 sudo mount /dev/sdc2 /mnt/public