Improvement: Added JavaDocs to TargetRollModifier Class & Constructor to Reduce Ambiguity (MegaMek#7491)

As per title. Nothing exciting here.

As further action, it might make sense to rename 'TargetRoll' and
'TargetRollModifier' to 'TargetNumber' and 'TargetNumberModifier' to
further reduce risk of confusion moving forward. Such confusion was the
root cause of MegaMek/mekhq#7713

Author: HammerGS

megamek/src/megamek/common/TargetRollModifier.java

@@ -42,9 +42,21 @@
  * This class represents individual modifiers for a {@link TargetRoll}. Each modifier has a value, the actual modifier
  * like +1 or -2 or one of the finalizers like {@link TargetRoll#AUTOMATIC_FAIL}, a description (attacker jumped) and
  * indicates if it is cumulative. Note: This class is immutable.
+ *
+ * <p><b>WARNING:</b> it is important to note that this is a modifier to the <b>Target Number</b> and <i>not</i>
+ * the roll. That means that a {@code positive number} is bad and a {@code negative number} is good.</p>
  */
 public record TargetRollModifier(int value, String description, boolean cumulative) implements Serializable {
 
+    /**
+     * Constructs a {@link TargetRollModifier} with the specified value and description.
+     *
+     * <p><b>WARNING:</b> it is important to note that this is a modifier to the <b>Target Number</b> and <i>not</i>
+     * the roll. That means that a {@code positive number} is bad and a {@code negative number} is good.</p>
+     *
+     * @param value       the numeric value of the modifier
+     * @param description a description of the modifier's purpose or source
+     */
     public TargetRollModifier(int value, String description) {
         this(value, description, true);
     }