Add :config-reload to configuration docs (#11086)

Co-authored-by: Michael Davis <[email protected]>

book/src/configuration.md

@@ -27,8 +27,8 @@ hidden = false
 
 You can use a custom configuration file by specifying it with the `-c` or
 `--config` command line argument, for example `hx -c path/to/custom-config.toml`.
-Additionally, you can reload the configuration file by sending the USR1
-signal to the Helix process on Unix operating systems, such as by using the command `pkill -USR1 hx`.
+You can reload the config file by issuing the `:config-reload` command. Alternatively, on Unix operating systems, you can reload it by sending the USR1
+signal to the Helix process, such as by using the command `pkill -USR1 hx`.
 
 Finally, you can have a `config.toml` local to a project by putting it under a `.helix` directory in your repository.
 Its settings will be merged with the configuration directory `config.toml` and the built-in configuration.