[ci skip] Add issue template

.github/issue_template.md

+Hi! Thanks for using Jupyter's docker-stacks images.
+
+If you are requesting a library upgrade or addition in one of the existing images, please state the desired library name and version of the library here.
+
+If you are reporting an issue with one of the existing images, please answer the questions below to help us troubleshoot the problem. Please be as thorough as possible.
+
+**What docker image you are using?**
+
+Example: `jupyter/scipy-notebook`
+
+**What complete docker command do you run to launch the container (omitting sensitive values)?**
+
+Example: `docker run -it --rm -p 8889:8888 jupyter/all-spark-notebook:latest`
+
+**What steps do you take once the container is running to reproduce the issue?**
+
+Example:
+
+1. Visit http://localhost:8889
+2. Start an R noteobok
+3. ...