Add colours to Pkl errors in Cli output

To make error messages from Pkl eval easier to read, this change uses
the Jansi library to colour the output, making it quicker and easier to
scan error messages and understand what's happened.

The Jansi library also detects if the CLI output is a terminal capable
of handling colours, and will automatically strip out escape codes if
the output won't support them (e.g. piping the output somewhere else).

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/CliMain.kt

@@ -17,6 +17,7 @@ package org.pkl.commons.cli
 
 import java.io.PrintStream
 import kotlin.system.exitProcess
+import org.fusesource.jansi.AnsiConsole
 
 /** Building block for CLIs. Intended to be called from a `main` method. */
 fun cliMain(block: () -> Unit) {
@@ -27,6 +28,9 @@ fun cliMain(block: () -> Unit) {
     if (!message.endsWith('\n')) stream.println()
   }
 
+  // Setup AnsiConsole. This will automatically strip escape codes if
+  // the target shell doesn't appear to support them.
+  AnsiConsole.systemInstall()
   // Force `native-image` to use system proxies (which does not happen with `-D`).
   System.setProperty("java.net.useSystemProxies", "true")
   try {