Add capacity on Event (#199)

Added capacity as a return value for events

https://nylas.atlassian.net/browse/TW-2509

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src/main/kotlin/com/nylas/models/Event.kt

@@ -135,6 +135,11 @@ data class Event(
    */
   @Json(name = "html_link")
   val htmlLink: String? = null,
+  /**
+   * The maximum number of participants that may attend the event
+   */
+  @Json(name = "capacity")
+  val capacity: Int? = null,
 ) {
   /**
    * Get the type of object.