message: Fix ParticleContainer type issues
diff: @@ -45,7 +45,7 @@ export interface IParticleProperties {
  */
  export class ParticleContainer extends Container
  {
  - public readonly blendMode: BLEND_MODES;
  + public blendMode: BLEND_MODES;
  public autoResize: boolean;
  public roundPixels: boolean;
  public baseTexture: BaseTexture;
  @@ -73,7 +73,7 @@ export class ParticleContainer extends Container
  * @param {boolean} [autoResize=false] - If true, container allocates more batches in case
  * there are more than `maxSize` particles.
  */
  - constructor(maxSize = 1500, properties: IParticleProperties, batchSize = 16384, autoResize = false)
  + constructor(maxSize = 1500, properties?: IParticleProperties, batchSize = 16384, autoResize = false)
  {
  super();
  