Customize color/width of detection box overlay

[leigh-johnson]

Describe your Request
Right now, we draw a bounding box overlay using the tensor_decoder element from the nnstreamer plugin package. The default is a blue color with 1 pixel border-width.

https://nnstreamer.github.io/gst/nnstreamer/elements/gsttensor_decoder.html

We would need to extend the tensor_decoder element to accept color, border-width parameters. Looks like this is already on the nnstreamer todo list:
https://github.com/nnstreamer/nnstreamer/blob/main/ext/nnstreamer/tensor_decoder/tensordec-boundingbox.c#L875