Adding function to get filegroup information

[sqllensman]

Type of Change

• Bug fix (non-breaking change, fixes #)
• New feature (non-breaking change, adds functionality)
• Breaking change (effects multiple commands or functionality)
• Ran manual Pester test and has passed (`.\tests\manual.pester.ps1)
• Adding code coverage to existing functionality
• Pester test is included
• If new file reference added for test, has is been added to github.com/sqlcollaborative/appveyor-lab ?
• Nunit test is included
• Documentation
• Build system

Purpose

Add functions to get SMO Filegroup information
Similar to Get-DbaDBTable and Get-DbaDatabase

Commands to test

Get-DbaDbFileGroup

[potatoqualitee]

Excellent PR, thank you so much! 💯

[potatoqualitee]

sweet af thank you! please note that future commands should not include aliases for the params. i think i removed that from the template but maybe not 🤔