text: Title: MixVisionTransformer in combination with PAN fails with "encoder does not support dilated mode"
  Body: ```
  import segmentation_models_pytorch as smp
  
  smp.PAN(encoder_name="mit_b0")
  ```
  raises the exception:
  ```
  ValueError: MixVisionTransformer encoder does not support dilated mode
  ```
  
  Since the default PAN uses dilation, this config is uncompatible atm?
  
  If we use a configuration of PAN that does not use dilation the error, of course, does not apper:
  ```
  smp.PAN(encoder_name="mit_b0", encoder_output_stride=32)
  ```
  I did not test yet though if output strides of 32 still deliver comparable results. My guess would be that the default stride of 16 should encode a lot more of information that might be beneficial for better performence.
  
  Is there any way to get it to work with dilation?