Update issue templates

.github/ISSUE_TEMPLATE/training-issue---no-detections---nan-avg-loss---low-accuracy.md

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+---
+name: Training issue - no-detections / Nan avg-loss / low accuracy
+about: Training issue - no-detections / Nan avg-loss / low accuracy
+title: ''
+labels: Training issue
+assignees: ''
+
+---
+
+If you have an issue with training - no-detections / Nan avg-loss / low accuracy:
+    * what command do you use?
+    * what dataset do you use?   
+    * what Loss and mAP did you get?
+    * show chart.png with Loss and mAP    
+    * check your dataset - run training with flag `-show_imgs` i.e. `./darknet detector train ... -show_imgs` and look at the `aug_...jpg` images, do you see correct truth bounded boxes?
+    * rename your cfg-file to txt-file and drag-n-drop (attach) to your message here
+    * show content of generated files `bad.list` and `bad_label.list` if they exist
+    * Read `How to train (to detect your custom objects)` and `How to improve object detection` in the Readme: https://github.com/AlexeyAB/darknet/blob/master/README.md
+    * show such screenshot with info
+```
+./darknet detector test cfg/coco.data cfg/yolov4.cfg yolov4.weights data/dog.jpg
+ CUDA-version: 10000 (10000), cuDNN: 7.4.2, CUDNN_HALF=1, GPU count: 1
+ CUDNN_HALF=1
+ OpenCV version: 4.2.0
+ 0 : compute_capability = 750, cudnn_half = 1, GPU: GeForce RTX 2070
+net.optimized_memory = 0
+mini_batch = 1, batch = 8, time_steps = 1, train = 0
+   layer   filters  size/strd(dil)      input                output
+```