Update ImageSlider so that descriptive alt text can be assigned to each image

[LawrenceQiu]

Summary

What is the nature of this pull request?

• New feature
• Enhancement to an existing feature
• Bug fix
• Configuration update
• Dependency update

Description of change

Created an array of strings to support alt text for each image.
Planning to further update this component to fully adhere to accessibility standards (Buttons must have discernible text).

Planner card link

(https://teams.microsoft.com/l/entity/com.microsoft.teamspace.tab.planner/tt.c_19:[email protected]_p_TOGdCftBI0mZ937fEIW0jsgAHPsL_h_1710632381880?tenantId=d02378ec-1688-46d5-8540-1c28b5f470f6&webUrl=https%3A%2F%2Ftasks.teams.microsoft.com%2Fteamsui%2FpersonalApp%2Falltasklists&context=%7B%22subEntityId%22%3A%22%2Fv1%2Fplan%2FTOGdCftBI0mZ937fEIW0jsgAHPsL%2Ftask%2FnQ2T2lPRA0aOw8DeLNIMk8gADgFG%22%2C%22channelId%22%3A%2219%3Ac1b94839a3db4c6e8bf052aeadb33d9b%40thread.tacv2%22%7D)

Readiness

• The application runs successfully with my change.
• I have included code comments where appropriate.
• Where I have copied and pasted code from other sources, I have included a comment with a link to the original source.
• I have read and followed the principles and guidelines about submitting code.
• I have added unit tests for new components and/or functionality.
• All existing and new unit tests pass (including updating tests for any necessary breaking changes).

[doubleedesign]

Once unit tests are passing, I'm happy with this :)