Update narou script

Specify "documents" sub-directory to docker like "-v
/mnt/Kindle/documents:/mnt/Kindle/documents" to avoid docker under WSL2
problem.  Also update README and version.

Makefile

@@ -1,5 +1,5 @@
 
-RELEASE_VERSION = v1.15
+RELEASE_VERSION = v1.16
 VERSION = latest
 
 OPTIONS = \

README.md

@@ -15,8 +15,8 @@ $ docker run --rm jam7/narou > narou
 $ chmod a+x narou
 ```
 
-Don't add `-ti` to `docker run`.  Otherwise, you may create a narou
-script with crlf.
+Don't add `-ti` to `docker run`.  Otherwise, your narou script may contains
+crlf.
 
 Run a generated script to download AozoraEpub3 to `$HOME/.narou/AozoraEpub3*`
 and initialize environment for narou.rb.
@@ -66,7 +66,7 @@ From WSL2, perform mount first.
 
 ```
 $ sudo mkdir -p /mnt/Kindle
-$ sudo mount -t drvfs D: /mnt/Kindle
+$ sudo mount -t drvfs d:/ /mnt/Kindle
 ```
 
 Then, use `narou send`.
@@ -75,10 +75,15 @@ Then, use `narou send`.
 $ narou send
 ```
 
-Unmount them.  This may takes for a while.
+Unmount them.  It is required to run umount three times on Ubuntu-20.04 with
+WSL2.
 
 ```
-$ sudo umount /mnt/Kindle
+$ sudo umount d:/
+$ sudo umount d:/
+$ sudo umount d:/
+$ sudo umount d:/
+umount: d:/: no mount point specified.
 ```
 
 ### Run as web service (not tested recently)

narou.sh

@@ -54,11 +54,23 @@ xinit)
   ;;
 esac
 
+if [ -d /mnt/Kindle/documents ]; then
+  MNT_KINDLE_OPT="-v"
+  MNT_KINDLE="/mnt/Kindle/documents:/mnt/Kindle/documents"
+else
+  MNT_KINDLE_OPT=""
+  MNT_KINDLE=""
+fi
+
 # Need to mount docker.sock in order to use jam7/kindlegen docker image.
+# Need to mount kindle device also.
+#   '-v /mnt/Kindle:/mnt/Kindle' rarely works.
+#   '-v /mnt/Kindle/documents:/mnt/Kindle/documents' works.
+#   Related issue: https://github.com/docker/for-win/issues/2151
 docker run $TTY --rm $opt \
     -v /var/run/docker.sock:/var/run/docker.sock \
     -v $data:/opt/narou \
-    -v /mnt/Kindle/:/mnt/Kindle \
+    $MNT_KINDLE_OPT $MNT_KINDLE \
     -e NAROU_UID="$( id -u )" \
     -e NAROU_GID="$( id -g )" \
     -e NAROU_USER="$( id -un )" \