Add Javadoc for new overloads (#4727)

Signed-off-by: Jacob Laursen <jacob-github@vindvejr.dk>

bundles/org.openhab.core.thing/src/main/java/org/openhab/core/thing/Thing.java

@@ -248,5 +248,10 @@ public interface Thing extends Identifiable<ThingUID> {
      */
     void setSemanticEquipmentTag(@Nullable String semanticEquipmentTag);
 
+    /**
+     * Set the semantic (equipment) tag of the {@link Thing}.
+     *
+     * @param semanticEquipmentTag the semantic (equipment) tag or {@code null} if no tag has been configured.
+     */
     void setSemanticEquipmentTag(@Nullable SemanticTag semanticEquipmentTag);
 }

bundles/org.openhab.core.thing/src/main/java/org/openhab/core/thing/binding/builder/ThingBuilder.java

@@ -266,6 +266,12 @@ public class ThingBuilder {
         return this;
     }
 
+    /**
+     * Set the semantic (equipment) tag for this thing
+     *
+     * @param semanticEquipmentTag semantic (equipment) tag for this thing
+     * @return the {@link ThingBuilder} itself
+     */
     public ThingBuilder withSemanticEquipmentTag(SemanticTag semanticEquipmentTag) {
         return withSemanticEquipmentTag(semanticEquipmentTag.getName());
     }