Add companion utility to transfer clipboard contents to/from Xsunaba sandbox X session

[morgant]

I've had some WIP documentation kicking around re:transferring clipboard contents to/from the Xsunaba X session using xclip(1):

index 1d0a370..d55770a
--- a/README.md
+++ b/README.md
@@ -29,6 +29,7 @@ Limitations due to implementation via `Xephyr`:
 
 ### Optional
 
+* [xclip(1)](https://github.com/astrand/xclip)
 * [sndio(7)](https://man.openbsd.org/sndio)
 
 ## INSTALLATION
@@ -82,6 +83,25 @@ You can then execute `Xsunaba` with your custom sandbox user, for example (repla

XSUNABA_USER=<sandbox_user> Xsunaba firefox --private-window &

+<<<<<<< Updated upstream
+=======
+
+#### Shared Selection and/or Clipboard
+
+If you want to copy the sandbox user's X selection and/or clipboard to your user's selection and/or clipboard, this can be done with `xclip`. After starting an application in your `Xsunaba` sandbox, do the following:
+
+##### Selection
+
+```+doas -u "$XSUNABA_USER" xclip -display "$XSUNABA_DISPLAY" -out | xclip -in
+```
+
+##### Clipboard
+
+```
+doas -u "$XSUNABA_USER" xclip -display "$XSUNABA_DISPLAY" -selection clipboard -out | xclip -selection clipboard -in
+```
+>>>>>>> Stashed changes

#### Shared Files

I'm thinking that it might be preferable to have a companion script/utility to perform such actions. I'd probably want to structure the options/commands/parameters in such a way that its use might later be extended to copying files to/from the sandbox, as well.

I've thought a little bit about the name of such a utility as I want it to be shorter than something like XsunabaClip. One consideration is Xoke, a portmanteau of 'X' and 'oke' (romaji for '桶', which translates to 'bucket' or 'pail', the tool one would use to transfer the contents — sand — to/from a sandbox) I want to do some research to make sure it 'xoke' doesn't mean anything in any other languages.