Make the issue status bar item optional

See merge request fatihacet/gitlab-vscode-extension!4

Closes #22

Closes #20

Closes #24

Closes #25

This may not be the best solution, for now favor boring solution.

Thank you @swiffer 👍

# Conflicts:
#	README.md

Fix handling of subgroups per #16

See merge request fatihacet/gitlab-vscode-extension!3

Fixes #17.

We will use fallback branch,

Thanks @kushalpandya.