Bump version from 1.9.8 to 1.9.9

Commits

• 50a4778: Bump version from 1.9.8 to 1.9.9 (Maxwell) #478
• f88f30e: Move grouping tests to test directory (Maxwell) #478,#477
• 60ed836: Add markdown mode preference toggle and strings resources (Maxwell) #478,#477
• 054fa38: Fix duplicate key titles for list style and de-translation format (Maxwell) #478,#477
• f69f945: Add additional translation keys for notifications and recommendations (Maxwell) #478,#477
• f7ed5b9: Remove redundant preference apply calls (Maxwell) #478,#477
• 2ba506e: Register experimental toggle to trigger app restart notice (Maxwell) #478,#477
• 72707bc: Enable StatusConetntWidget and perform conditional check for experimental mode (Maxwell) #478,#477
• 2e85fcf: Update changelog.md (Maxwell) #478,#477
• 5062c88: Update README.md (Maxwell Mapako) #478