readme: added usage & mount cmd example

README.md

@@ -7,6 +7,33 @@ make
 
 # Usage
 
+```sh
+rgpgfs -r [fingerprint] [mountpoint]
+# or
+rgpgfs --recipient=[fingerprint] [mountpoint]
+# or
+rgpgfs -o recipient=[fingerprint] [mountpoint]
+```
+
+## Example
+
+Mount encrypted view of `/` in `~/rgpgfs`:
+
+```sh
+$ rgpgfs --recipient 1234567890ABCDEF1234567890ABCDEF12345678 ~/rgpgfs
+
+$ ls -1 ~/rgpfs/var/log/syslog.*
+/home/me/rgpgfs/var/log/syslog.gpg
+/home/me/rgpgfs/var/log/syslog.1.gpg
+/home/me/rgpgfs/var/log/syslog.2.gz.gpg
+/home/me/rgpgfs/var/log/syslog.3.gz.gpg
+
+$ gpg --decrypt --for-your-eyes-only /home/me/rgpgfs/var/log/syslog.gpg | wc -l
+gpg: encrypted with 4096-bit RSA key, ID 89ABCDEF12345678, created 2019-03-30
+      "someone <someone@somewhere.me>"
+3141
+```
+
 ## Change source directory
 
 ```sh