GitLab feature package

Description

This MR focuses on GitLab features for the template, mainly mirroring already existing features for GitHub. Apart from implementing automatic releases and CHANGELOG updates for the template as it was done for the project previously, now it also leverages GitLab CI/CD components to implement stale issues using triage policies.

Related Issue

Closes #17 (closed), #19 (closed) and #34 (closed)