modify configurations and use 'global_encoder'

[Henry-Bi]

When attempting to utilize an additional global encoder implementation, I encountered an error despite modifying the 'use_global_encoder' parameter to 'True' in the 'conf/default.conf' file. The error message displayed is as follows:
pyhocon.exceptions.ConfigMissingException: 'No configuration setting found for key global_encoder
It appears that the aforementioned error arises due to the absence of a definition for the network architecture of the 'global_encoder'. To address this issue, I included the necessary 'global_encoder' configuration in the 'conf/default.conf' file, similar to how the 'encoder' is defined on lines 43-47, and this solution proved successful.

[Henry-Bi]

global_encoder {
    backbone = resnet34
    pretrained = True
    num_layers = 4
}