feat(issue): add issue-type filter to issue cmd

Description

Add an issue-type filter allowing filter issues by their issue_type. A user will be able to fetch the list of incidents only by using:

glab issue --issue_type=incident
glab issue -t incident

Related Issues

Resolves #1092 (closed)

How has this been tested?

1. I've run make build command from the CLI app directory
2. Run the app from another GitLab app directory /Users/vtatarintev/Developer/GitLab/cli/bin/glab issue list -t incident
3. Got the list of incidents

Screenshots (if appropriate):

glab issue

glab issue --issue-type=incident

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)