feat: Start work on interactive Shell

Author: MarcellPerger1

runshell.sh

@@ -0,0 +1 @@
+java -classpath ./target/classes/ net.marcellperger.mathexpr.interactive.Shell

src/main/java/net/marcellperger/mathexpr/interactive/Shell.java

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+package net.marcellperger.mathexpr.interactive;
+
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class Shell {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        System.out.println("args = " + Arrays.toString(args));
+        System.out.print("Enter something: ");
+        String s = sc.nextLine();
+        System.out.println("You entered " + s);
+    }
+}