tui: add README describing some debugging specifics

Signed-off-by: Christoph Heiss <c.heiss@proxmox.com>

proxmox-tui-installer/README.md

@@ -0,0 +1,28 @@
+# proxmox-tui-installer
+
+## Testing/debugging
+
+### stderr redirection
+
+If something needs to be printed for debugging (e.g. using `eprintln!()` or
+`dbg!()`), output redirection can be used. Open a second terminal and get the
+file name of the terminal using the `tty` command:
+```sh
+$ tty
+/dev/pts/6
+```
+
+Now, simply run the installer using:
+```sh
+$ cargo run 2>/dev/pts/6
+```
+
+All stderr output will then show up in the other terminal.
+
+### Specific terminal size
+
+To test the installer with a specific output size, the `stty` command can be
+used. For example, to set it to a standard 80x25 terminal:
+```sh
+$ stty columns 80 rows 25
+```