[chore] Upload issue templates

Upload 2 templates :
- feature request
- bugfix request

Those templates are used when creating an issue. Predefined sections make it easier to describe an issue (summary, current behavior, desired behavior, related things, sources, etc.)

.gitlab/issue_templates/bug_template.md

+## Summary
+
+(Summarize the bug encountered concisely)
+
+## Steps to reproduce
+
+(How one can reproduce the issue - this is very important)
+
+## Example Project
+
+(If possible, create an example project here on GitLab.com that exhibits the problematic
+behavior, and link to it here in the bug report.
+If you are using an older version of GitLab, this will also determine whether the bug has been fixed
+in a more recent version)
+
+## What is the current bug behavior?
+
+(What actually happens)
+
+## What is the expected correct behavior?
+
+(What you should see instead)
+
+## Relevant logs and/or screenshots
+
+(Paste any relevant logs - use code blocks (```) to format console output, logs, and code, as
+it's very hard to read otherwise.)
+
+## Possible fixes
+
+(If you can, link to the line of code that might be responsible for the problem)
+
+/label ~bug ~reproduced ~needs-investigation
+/cc @project-manager
+/assign @qa-tester
\ No newline at end of file

.gitlab/issue_templates/feature_request.md

+## Summary
+
+(Summarize the desired featured concisely)
+
+## Current behavior
+
+(Explain the current behavior of the software)
+
+## Desired behavior
+
+(Explain the expected behavior as specifically as possible, with examples, where files should be stored, details on data structure, applications, etc.)
+
+## Sources
+
+(Give relevant sources i.e. stackoverflow posts, scientific papers, etc.)
+
+## Linked features or branches
+
+(List relevant linked features and branches of the project, typically if this feature request is the child of another branch)
+
+