add initial security release template

.gitlab/issue_templates/Security Release.md

+<!--
+# Read me first!
+
+Set the title to: `Security Release: 11.4.X, 11.3.X, and 11.2.X`
+-->
+
+## Releases tasks
+
+- https://gitlab.com/gitlab-org/release/docs/blob/master/general/security/release-manager.md
+- https://gitlab.com/gitlab-org/release/docs/blob/master/general/security/developer.md
+- https://gitlab.com/gitlab-org/release/docs/blob/master/general/security/security-engineer.md
+
+## Version issues:
+
+* 11.5.X: {release task link}
+* 11.4.X: {release task link}
+* 11.3.X: {release task link}
+
+## Security Issues:
+
+### CE
+
+* {https://gitlab.com/gitlab-org/gitlab-ce/issues link}
+
+### EE
+
+* {https://gitlab.com/gitlab-org/gitlab-ee/issues link}
+
+## Security Issues in dev.gitlab.org:
+
+### CE
+
+- {https://dev.gitlab.org/gitlab/gitlabhq/issues link}
+
+| Version | MR | Status|
+|---------|----|-------|
+| 11.4 | {https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/ link} |  |
+| 11.3 | {https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/ link} |  |
+| 11.2 | {https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/ link} |  |
+| master | {https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/ link} |  |
+
+
+
+### EE
+
+* {https://dev.gitlab.org/gitlab/gitlabhq/issues/ link}
+
+
+| Version | MR | Status|
+|---------|----|-------|
+| 11.4| {https://dev.gitlab.org/gitlab/gitlab-ee/merge_requests/ link} |   |
+| 11.3 | {https://dev.gitlab.org/gitlab/gitlab-ee/merge_requests/ link} |  |
+| 11.2 | {https://dev.gitlab.org/gitlab/gitlab-ee/merge_requests/ link} |  |
+| master | {https://dev.gitlab.org/gitlab/gitlab-ee/merge_requests/ link} |  |
+
+
+## QA
+{QA issue link}
+
+## Blog post
+
+Dev: {https://dev.gitlab.org/gitlab/www-gitlab-com/merge_requests/ link}<br/>
+gitlab.com: {https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/ link}
+
+## Email notification
+{https://gitlab.com/gitlab-com/marketing/general/issues/ link}
+
+/label ~security
+/confidential