Fix Javadoc warnings

[javier-godoy]

Describe the bug

There are javadoc warnings

Expected behavior

No response

Minimal reproducible example

No response

Add-on Version

1.0.2-SNAPSHOT

Vaadin Version

Additional information

[WARNING] Javadoc Warnings
[WARNING] J:\fc\addons\DayOfWeekSelectorAddon\src\main\java\com\flowingcode\vaadin\addons\dayofweekselector\DayOfWeekSelector.java:195: warning: @return tag cannot be used in method with void return type.
[WARNING] public void setWeekDaysShort(List<String> weekdaysShort) {
[WARNING] ^
[WARNING] J:\fc\addons\DayOfWeekSelectorAddon\src\main\java\com\flowingcode\vaadin\addons\dayofweekselector\DayOfWeekSelector.java:212: warning: @param argument "firstDayOfWeek" is not a parameter name.
[WARNING] * @param firstDayOfWeek the index of the first day of the week
[WARNING] ^
[WARNING] J:\fc\addons\DayOfWeekSelectorAddon\src\main\java\com\flowingcode\vaadin\addons\dayofweekselector\DayOfWeekSelector.java:216: warning: @return tag cannot be used in method with void return type.
[WARNING] public void setFirstDayOfWeek(DayOfWeek first) {