message: Add two missing global methods for TextureLoader
diff: +/* -------------------------------------------- */
  +
  +/**
  + * Test whether a file source exists by performing a HEAD request against it
  + * @param src - The source URL or path to test
  + * @returns Does the file exist at the provided url?
  + */
  +declare function srcExists (src: string): boolean
  +
  +/* -------------------------------------------- */
  +
  +/**
  + * Get a single texture from the cache
  + */
  +declare function getTexture (src: string): PIXI.Texture
  +
  /**
  * Load a single texture and return a Promise which resolves once the texture is ready to use
  * @param src - The requested texture source
  