Improve javadoc for some addons (#15701)

Signed-off-by: Holger Friedrich <mail@holger-friedrich.de>

bundles/org.openhab.binding.icalendar/src/main/java/org/openhab/binding/icalendar/internal/logic/AbstractPresentableCalendar.java

@@ -25,7 +25,7 @@ import org.eclipse.jdt.annotation.Nullable;
  * the binding, encapsulating the implementation of the real calendar.
  *
  * @author Michael Wodniok - Initial contribution
- * @author Andrew Fiddian-Green - Methods getJustBegunEvents() & getJustEndedEvents()
+ * @author Andrew Fiddian-Green - Methods getJustBegunEvents() and getJustEndedEvents()
  * @author Michael Wodniok - Added getFilteredEventsBetween()
  */
 @NonNullByDefault

bundles/org.openhab.binding.icalendar/src/main/java/org/openhab/binding/icalendar/internal/logic/CommandTag.java

@@ -36,10 +36,14 @@ import org.slf4j.LoggerFactory;
  * This is a class that implements a Command Tag that may be embedded in an
  * Event Description. Valid Tags must follow one of the following forms..
  *
+ * <pre>
+ * {@code
  * BEGIN:<itemName>:<targetState>
  * BEGIN:<itemName>:<targetState>:<authorizationCode>
  * END:<itemName>:<targetState>
  * END:<itemName>:<targetState>:<authorizationCode>
+ * }
+ * </pre>
  *
  * @author Andrew Fiddian-Green - Initial contribution
  */

bundles/org.openhab.binding.icalendar/src/main/java/org/openhab/binding/icalendar/internal/logic/CommandTagType.java

@@ -18,8 +18,12 @@ import org.eclipse.jdt.annotation.Nullable;
 /**
  * A type enumerator to indicate whether a Command Tag is of type BEGIN or END; as in the following examples:
  *
+ * <pre>
+ * {@code
  * BEGIN:<item_name>:<new_state>
  * END:<item_name>:<new_state>
+ * }
+ * </pre>
  *
  * @author Andrew Fiddian-Green - Initial contribution
  */