Fix file name. Add shared to files

[VladislavAntonyuk]

Description of Change

Fix file name to be consistent through the whole solution.

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pulls/XYZ

Additional information

[brminnick]

Thanks Vlad! I opened a Discussion to see if there's a way to ensure we don't get any invalid file suffixes in the future too!