[iOS] Add podspec for ListItem

[alexanderboswell]

Platforms Impacted

• [X] iOS
• [ ] macOS

Description of changes

Add ListItem in the podspec file so it can be consumed.

Microsoft Reviewers: Open in CodeFlow

[alexanderboswell]

@huwilkes When I created the ListItem it seemed ideal to use the same tokens as TableViewCell. I do wonder if that doesnt make as much sense anymore because it is required for ListItem - which makes it so you have more needed (which is easy to see now when we define the podspec)

Thoughts?

[huwilkes]

@huwilkes When I created the ListItem it seemed ideal to use the same tokens as TableViewCell. I do wonder if that doesnt make as much sense anymore because it is required for ListItem - which makes it so you have more needed (which is easy to see now when we define the podspec)

Thoughts?

Probably makes sense to move the tokens into their own podspec that both list item and tvc depend on rather than adding a new identical token set.