Add new template file for bugs

.gitlab/issue_templates/.gitlab/issue_templates/bug.md

+# Reporters
+
+- name-of-proposer-1 (institution-of-proposer-1)
+- name-of-proposer-2 (institution-of-proposer-2)
+...
+
+# Description
+
+Describe the bug.
+If needed, Attach logs and reports to your bug.
+If needed, feel free to point external content as references (journal paper, Youtube video, etc.).
+
+## Deployment environment
+- Operating System (include version):
+- MicroK8s (include version and add-ons):
+- TeraFlowSDN (include release/branch-name/commit-id):
+
+
+## TFS deployment settings
+- list of components deployed
+- particular configurations you applied
+- any other particularity you might find important
+
+## Sequence of actions that resulted in the bug
+- be explicit and enumerate each step.
+- if possible, include example calls, request files, descriptor files, etc.
+
+## Document the explicit error
+- include the traceback of the error
+- include the log files of the components / scheenshoots of WebUI (attached files)
+- if known, include the list of TFS components affected by the bug
+
+## Expected behaviour
+- describe the expected behavior (if you know it)
+
+# References
+
+1. [Reference name](https://reference-url)
+2. Author1, Author2, Author3, et. al., “My demo using feature,” in Conference-Name Demo Track, 20XX.