text: Title: [bug] Opacity parameter not working in geemap.deck Layer API
  Body: ### Environment Information
  
  Tue Jan 28 16:21:45 2025 UTC
  --
  OS | Linux (Ubuntu 22.04) | CPU(s) | 2 | Machine | x86_64
  Architecture | 64bit | RAM | 12.7 GiB | Environment | IPython
  Python 3.11.11 (main, Dec 4 2024, 08:55:07) [GCC 11.4.0]
  geemap | 0.35.1 | ee | 1.4.6 | ipyleaflet | 0.19.2
  folium | 0.19.4 | jupyterlab | Module not found | notebook | 6.5.5
  ipyevents | 2.0.2 | geopandas | 1.0.1 |   |  
  
  
  
  ### Description
  
  Trying to draw an EE layer with transparency (partial opacity) using the `geemap.deck` extension module.
  
  
  The [geemap.deck.Layer.add_ee_layer](https://geemap.org/deck/#geemap.deck.Map.add_ee_layer) method’s documentation includes an `opacity` keyword argument which should allow setting the layer’s opacity.  This is often useful when there is a need for transparency to ensure a new layer doesn’t completely occlude other layers or the base map itself.
  
  However, this argument is currently [ignored in the implementation](https://github.com/gee-community/geemap/blob/824e4e5/geemap/deck.py#L103-L187) which can cause confusion for the user.    
  
  ### What I Did
  
  As an _undocumented_ workaround, I set the `opacity` within the `vis_params` dictionary explicitly to get the opacity to work.
  
  ```python
  import geemap.deck as gmd
  
  image_collection = ee.ImageCollection(...)
  
  vis_params = {
      "min": -40.0,
      "max": 35.0,
      "palette": ["blue", "purple", "cyan", "green", "yellow", "red"],
      # set within vis parameters instead of the add_ee_layer_kwarg
      "opacity": 0.2,
  }
  
  
  view_state = pdk.ViewState(,,,)
  m = gmd.Map(initial_view_state=view_state)
  
  # NOTE: opacity kwarg is not recognized.  rely on vis_params instead
  m.add_ee_layer(image_collection, vis_params=vis_params, ...)
  m.show()
  ```
  
  ~It would be a trivial fix to simply do this automatically within `add_ee_layer` to set the `opacity` within the `vis_params` dictionary if this kwarg is not `None`.~
  