refactor: add getter for TerminalConsole prompt

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/xterm/ITerminalConsole.java

@@ -73,6 +73,11 @@ default void setPrompt(String prompt) {
     getElement().setProperty("prompt", prompt);
   }
 
+  /** Returns the command line prompt. */
+  default String getPrompt() {
+    return getElement().getProperty("prompt", "");
+  }
+
   /** Writes the command line prompt to the terminal. */
   default void writePrompt() {
     ((XTermBase) this).executeJs("this.writePrompt()");

src/main/java/com/flowingcode/vaadin/addons/xterm/TerminalHistory.java

@@ -109,7 +109,7 @@ private void handleArrowDown() {
   private void write(String line) {
     if (line != null) {
       // erase logical line, cursor home in logical line, cursor horizontal absolute
-      String prompt = terminal.getElement().getProperty("prompt", "");
+      String prompt = ((ITerminalConsole) terminal).getPrompt();
       terminal.write("\033[<2K\033[<H\033[G" + prompt + line);
       lastRet = line;
     }